debug_backtrace()

(PHP 4 >= 4.3.0, PHP 5, PHP 7)

产生一条回溯跟踪(backtrace)

说明

debug_backtrace([int $options= DEBUG_BACKTRACE_PROVIDE_OBJECT[,int $limit= 0]]): array

debug_backtrace()产生一条 PHP 的回溯跟踪(backtrace)。

参数

$options

截至 5.3.6，这个参数是以下选项的位掩码：

debug_backtrace()选项

DEBUG_BACKTRACE_PROVIDE_OBJECT	是否填充"object"的索引。
DEBUG_BACKTRACE_IGNORE_ARGS	是否忽略"args"的索引，包括所有的 function/method 的参数，能够节省内存开销。

在 5.3.6 之前，仅仅能使用的值是TRUE或者FALSE，分别等于是否设置DEBUG_BACKTRACE_PROVIDE_OBJECT选项。

$limit

截至 5.4.0，这个参数能够用于限制返回堆栈帧的数量。默认为($limit=0)，返回所有的堆栈帧。

返回值

返回一个包含众多关联数组的array。以为为有可能返回的元素：

更新日志

范例

Example #1debug_backtrace()范例

<?php
// filename: /tmp/a.php
function a_test($str)
{
    echo "\nHi: $str";
    var_dump(debug_backtrace());
}
a_test('friend');
?>
<?php
// filename: /tmp/b.php
include_once '/tmp/a.php';
?>

执行/tmp/b.php返回的结果类似于以下：

Hi: friend
array(2) {
[0]=>
array(4) {
    ["file"] => string(10) "/tmp/a.php"
    ["line"] => int(10)
    ["function"] => string(6) "a_test"
    ["args"]=>
    array(1) {
      [0] => &string(6) "friend"
    }
}
[1]=>
array(4) {
    ["file"] => string(10) "/tmp/b.php"
    ["line"] => int(2)
    ["args"] =>
    array(1) {
      [0] => string(10) "/tmp/a.php"
    }
    ["function"] => string(12) "include_once"
  }
}

参见

• trigger_error() 产生一个用户级别的 error/warning/notice 信息
• debug_print_backtrace() 打印一条回溯。

Here's a function I just wrote for getting a nice and comprehensible call trace. It is probably more resource-intensive than some other alternatives but it is short, understandable, and gives nice output (Exception->getTraceAsString()).
<?php
function generateCallTrace()
{
  $e = new Exception();
  $trace = explode("\n", $e->getTraceAsString());
  // reverse array to make steps line up chronologically
  $trace = array_reverse($trace);
  array_shift($trace); // remove {main}
  array_pop($trace); // remove call to this method
  $length = count($trace);
  $result = array();
  
  for ($i = 0; $i < $length; $i++)
  {
    $result[] = ($i + 1) . ')' . substr($trace[$i], strpos($trace[$i], ' ')); // replace '#someNum' with '$i)', set the right ordering
  }
  
  return "\t" . implode("\n\t", $result);
}
?>
Example output:
  1) /var/www/test/test.php(15): SomeClass->__construct()
  2) /var/www/test/SomeClass.class.php(36): SomeClass->callSomething()

Just a short note on debug_backtrace options for PHP 5.3.6 or newer:
debug_backtrace() - show all options
debug_backtrace(0) - exlude ["object"]
debug_backtrace(1) - same as debug_backtrace()
debug_backtrace(2) - exlude ["object"] AND ["args"]
use this example and try calling debug_backtrace with different options
<?php
function F1()
{
  echo "<br />";
  echo "in F1 now";
  echo "<pre>".print_r(debug_backtrace(2),true)."</pre>";
}
class DebugOptionsTest
{
  function F2()
  {
    echo "<br />";
    echo "in F2 now";
    F1();
  }
}
echo "<hr />calling F1";
F1();
$c=new DebugOptionsTest();
echo "<hr /><hr /><hr />calling F2";
$c->F2("testValue");
?>

If you are using the backtrace function in an error handler, avoid using var_export() on the args, as you will cause fatal errors in some situations, preventing you from seeing your stack trace. Some structures will cause PHP to generate the fatal error "Nesting level too deep - recursive dependency?" This is a design feature of php, not a bug (see http://bugs.php.net/bug.php?id=30471)

Simple function to get a string in form "filename: [class->][function(): ]"
<?php
function get_caller_info() {
  $c = '';
  $file = '';
  $func = '';
  $class = '';
  $trace = debug_backtrace();
  if (isset($trace[2])) {
    $file = $trace[1]['file'];
    $func = $trace[2]['function'];
    if ((substr($func, 0, 7) == 'include') || (substr($func, 0, 7) == 'require')) {
      $func = '';
    }
  } else if (isset($trace[1])) {
    $file = $trace[1]['file'];
    $func = '';
  }
  if (isset($trace[3]['class'])) {
    $class = $trace[3]['class'];
    $func = $trace[3]['function'];
    $file = $trace[2]['file'];
  } else if (isset($trace[2]['class'])) {
    $class = $trace[2]['class'];
    $func = $trace[2]['function'];
    $file = $trace[1]['file'];
  }
  if ($file != '') $file = basename($file);
  $c = $file . ": ";
  $c .= ($class != '') ? ":" . $class . "->" : "";
  $c .= ($func != '') ? $func . "(): " : "";
  return($c);
}
?>
Usage like:
<?php
function debug($str) {
  echo get_caller_info() . $str . "<br>\n";
}
?>
get_caller_info() will return info about the function /class->method that called debug().

When using debug_backtrace() to check if you're being accessed from another caller, please remember to ask debug_backtrace to only go as far as needed in depth and skip taking the entire debug object as return parameter:
<?php
  if (count(debug_backtrace(FALSE, 1)) == 0)
  {
    // Do something
  }
?>

One line of code to print simplest and shortest human readable backtrace:)
<?php
array_walk(debug_backtrace(),create_function('$a,$b','print "{$a[\'function\']}()(".basename($a[\'file\']).":{$a[\'line\']}); ";'));
?>

Quick and dirty formatted output from debug_backtrace.
$file_paths = debug_backtrace();
 
foreach($file_paths AS $file_path) {
 foreach($file_path AS $key => $var) {
  if($key == 'args') {
   foreach($var AS $key_arg => $var_arg) {
    echo $key_arg . ': ' . $var_arg . '<br>';
   }
  } else {
   echo $key . ': ' . $var . '<br>';
  } 
 }
}

When use register_shutdown_function, and the function called when shutting down, there are no line number nor filename information about this function, only function, class(if possible), type(if possible) and args are provided.

A usual entry looks like this:
<?php
array(6) {
 'file' =>
 string(87) "DbSelector.php"
 'line' =>
 int(171)
 'function' =>
 string(5) "error"
 'class' =>
 string(42) "LoggingService"
 'type' =>
 string(2) "::"
 'args' =>
 array(1) {
  [0] =>
  string(27) "Connecting to DB: unittests"
 }
}
?>
Be warned though that 'file' and 'class' do not reference the same thing!
'file' means which file calls the next step.
'class' is the next step being called.
So 'file' is the caller, 'class' is the callee.

Here's my little updated contribution - it prints colorful output in the way I prefer. Define a helper function isRootIp() that contains an array including your IP; then calls to bt() simply return, so you can sprinkle backtraces in live sites w/o anyone knowing.
<?php
function bt()
{
  if( ! isRootIp() )
  {
    return false;
  }
  array_walk( debug_backtrace(), create_function( '$a,$b', 'print "<br /><b>". basename( $a[\'file\'] ). "</b> &nbsp; <font color=\"red\">{$a[\'line\']}</font> &nbsp; <font color=\"green\">{$a[\'function\']} ()</font> &nbsp; -- ". dirname( $a[\'file\'] ). "/";' ) );
}
?>

Here is a function to cleanly output the debug_backtrace to the error_log
<?php
/*
 * Send the output from a backtrace to the error_log
 * @param string $message Optional message that will be sent the the error_log before the backtrace
 */
function log_trace($message = '') {
  $trace = debug_backtrace();
  if ($message) {
    error_log($message);
  }
  $caller = array_shift($trace);
  $function_name = $caller['function'];
  error_log(sprintf('%s: Called from %s:%s', $function_name, $caller['file'], $caller['line']));
  foreach ($trace as $entry_id => $entry) {
    $entry['file'] = $entry['file'] ? : '-';
    $entry['line'] = $entry['line'] ? : '-';
    if (empty($entry['class'])) {
      error_log(sprintf('%s %3s. %s() %s:%s', $function_name, $entry_id + 1, $entry['function'], $entry['file'], $entry['line']));
    } else {
      error_log(sprintf('%s %3s. %s->%s() %s:%s', $function_name, $entry_id + 1, $entry['class'], $entry['function'], $entry['file'], $entry['line']));
    }
  }
}
?>

need no Xdebug or dbg.so on server, return more detailed message:
diyism_trace.php:
<?php
define(TRACES_MODE, 'TEXTAREA');//'TEXTAREA' or 'FIREPHP'
$GLOBALS['traces.pre']=array();
function my_array_diff($arr1, $arr2)
     {foreach ($arr1 as $k=>$v)
         {if (in_array($v, $arr2, true))
           {unset($arr1[$k]);
           }
         }
     return $arr1;
     }
function my_var_export($var, $is_str=false)
     {$rtn=preg_replace(array('/Array\s+\(/', '/\[(\d+)\] => (.*)\n/', '/\[([^\d].*)\] => (.*)\n/'), array('array (', '\1 => \'\2\''."\n", '\'\1\' => \'\2\''."\n"), substr(print_r($var, true), 0, -1));
     $rtn=strtr($rtn, array("=> 'array ('"=>'=> array ('));
     $rtn=strtr($rtn, array(")\n\n"=>")\n"));
     $rtn=strtr($rtn, array("'\n"=>"',\n", ")\n"=>"),\n"));
     $rtn=preg_replace(array('/\n +/e'), array('strtr(\'\0\', array(\'  \'=>\' \'))'), $rtn);
     $rtn=strtr($rtn, array(" Object',"=>" Object'<-"));
     if ($is_str)
       {return $rtn;
       }
     else
       {echo $rtn;
       }
     }
function tick_handler()
     {$tmp=debug_backtrace();
     $trace=my_array_diff($tmp, $GLOBALS['traces.pre']);
     //echo '<pre>';var_export($trace);echo '</pre>';echo '<br/>'; //for debug diyism_trace.php
     $trace=array_values($trace);
     $GLOBALS['traces.pre']=$tmp;
     if (count($trace)>0 && $trace[0]['file'].'/'.@$tmp[1]['function']!==@$GLOBALS['traces'][count($GLOBALS['traces'])-1]['key']) //filter empty array and rearrange array_values(), because some lines will trigger two tick events per line, for example: 1.last line is "some code;questmark>" 2.error_reporting(...
       {for ($i=count($trace)-1; $i>=0; --$i)
         {$GLOBALS['traces'][]=$tmp_fb=array_merge(array('key'=>$trace[$i]['file'].'/'.@$tmp[$i+1]['function']), $trace[$i], array('function'=>strtr($trace[$i]['function'], array('tick_handler'=>'CONTINUE')), 'in_function'=>@$tmp[$i+1]['function']));
          TRACES_MODE==='FIREPHP'?fb(trace_output($tmp_fb), 'diyism_trace:'.++$GLOBALS['diyism_trace_no']):'';
         }
       }
     }
function trace_output($trace)
     {$trace['in_function']=strtr(@$trace['in_function'], array('require'=>'', 'require_once'=>'', 'include'=>'', 'include_once'=>''));
     $trace['args']=$trace['args']?strtr(preg_replace(array('/\n +/'), array(''), preg_replace(array('/\n \d+ => /'), array(''), substr(my_var_export($trace['args'], true), 7, -3))), array("\r"=>'\r', "\n"=>'\n')):'';
     return $trace['file'].($trace['in_function']?'/'.$trace['in_function'].'()':'').'/'.$trace['line'].': '.$trace['function'].'('.$trace['args'].')';
     }
function traces_output()
     {echo '<textarea style="width:100%;height:300px;">';
     $GLOBALS['traces']=array_slice($GLOBALS['traces'], 2);//remove registering tick line and requiring 'diyism_trace.php' line
     foreach ($GLOBALS['traces'] as $k=>$trace)
         {echo htmlentities($k.':'.trace_output($trace)."\n");
         }
     echo '</textarea>';
     }
register_tick_function('tick_handler');
TRACES_MODE==='TEXTAREA'?register_shutdown_function('traces_output'):'';
?>
test.php:
<?php
declare(ticks=1);
require 'diyism_trace.php';
a('a', array('hello'));
1+2;
b();
function a()
     {$d=1;
     b();
     $d=2;
     }
function b()
     {1+1;
     }
?>

I want to point out that debug_backtrace() in new versions of php can detect recursion // circular references .. avoiding memory consumption.
Example:
<?php
class ParentClass {
    public function __construct() 
    {
        $this->_child = new ChildClass($this);
        var_dump(debug_backtrace());
    }
}
class ChildClass {
    public function __construct(ParentClass $p)
    {
        $this->_parent = $p;
    }
}
$test = new ParentClass();
?>
Output:
array(1) {
 [0]=>
 array(7) {
  ["file"]=>
  string(23) "/home/jcm/testdebug.php"
  ["line"]=>
  int(18)
  ["function"]=>
  string(11) "__construct"
  ["class"]=>
  string(11) "ParentClass"
  ["object"]=>
  object(ParentClass)#1 (1) {
   ["_child"]=>
   object(ChildClass)#2 (1) {
    ["_parent"]=>
    *RECURSION*
   }
  }
  ["type"]=>
  string(2) "->"
  ["args"]=>
  array(0) {
  }
 }
}
Attention in the *RECURSION* hint provided

The `args` element contains only the arguments actually passed to the function or method. It does not include default parameters if they were not explicitly specified. (A least, this is the case with PHP 7.1.9.) This is consistent with the behaviour of `func_get_args()`.

Be carefull if you are using objects as arguments for function calls!
<?php
error_reporting(E_ALL);
function myPrint($trace){
  foreach($trace as $i=>$call){
    /**
     * THIS IS NEEDED! If all your objects have a __toString function it's not needed!
     * 
     * Catchable fatal error: Object of class B could not be converted to string
     * Catchable fatal error: Object of class A could not be converted to string
     * Catchable fatal error: Object of class B could not be converted to string
     */
    if (is_object($call['object'])) { $call['object'] = 'CONVERTED OBJECT OF CLASS '.get_class($call['object']); }
    if (is_array($call['args'])) {
      foreach ($call['args'] AS &$arg) {
        if (is_object($arg)) { $arg = 'CONVERTED OBJECT OF CLASS '.get_class($arg); }
      }
    }
    
    $trace_text[$i] = "#".$i." ".$call['file'].'('.$call['line'].') ';
    $trace_text[$i].= (!empty($call['object'])?$call['object'].$call['type']:'');
    $trace_text[$i].= $call['function'].'('.implode(', ',$call['args']).')';
  }
  
  var_dump($trace_text);
}
class A{
  public function test($obj){
    $obj->test();
  }
}
class B{
  public function test(){
    echo myPrint(debug_backtrace());
  }
}
$A = new A();
$B = new B();
$A->test($B);
?>

It works a little bit different with resources in different PHP versions.
For example:
function foo($bar)
{
 return debug_backtrace();
}
$resource = fopen(__FILE__, 'r');
$backtrace = foo($resource);
echo "when resource is opened: " . gettype($backtrace[0]['args'][0]) . "\n";
fclose($resource);
echo "when resource is closed: " . gettype($backtrace[0]['args'][0]) . "\n";
With 5.3.10 I got:
when resource is opened: resource
when resource is closed: resource
With 5.5.9:
when resource is opened: resource
when resource is closed: unknown type
Be carefull.

Further to my previous note, the 'object' element of the array can be used to get the parent object. So changing the get_class_static() function to the following will make the code behave as expected:
<?php
  function get_class_static() {
    $bt = debug_backtrace();
  
    if (isset($bt[1]['object']))
      return get_class($bt[1]['object']);
    else
      return $bt[1]['class'];
  }
?>
HOWEVER, it still fails when being called statically. Changing the last two lines of my previous example to
<?php
 foo::printClassName();
 bar::printClassName();
?>
...still gives the same problematic result in PHP5, but in this case the 'object' property is not set, so that technique is unavailable.

Another variation formatting backtrace.
Parameter $ignore to ignore the extra calls.
<?php
/**
 * Getting backtrace
 *
 * @param int $ignore ignore calls
 *
 * @return string
 */
protected function getBacktrace($ignore = 2)
{
  $trace = '';
  foreach (debug_backtrace() as $k => $v) {
    if ($k < $ignore) {
      continue;
    }
    array_walk($v['args'], function (&$item, $key) {
      $item = var_export($item, true);
    });
    $trace .= '#' . ($k - $ignore) . ' ' . $v['file'] . '(' . $v['line'] . '): ' . (isset($v['class']) ? $v['class'] . '->' : '') . $v['function'] . '(' . implode(', ', $v['args']) . ')' . "\n";
  }
  return $trace;
}
?>

Howdy guys, just a note really - The ['args'] data within the resulting array is supplied by reference. I found myself editing the reference unknowingly which in turn shows its ugly head further down the line if you call multiple backtrace.
<?php
$trace = array_reverse(debug_backtrace());
// LOOP BACKTRACE
$la = 0;
$lb = count($trace);
while ($la<$lb){
  // DATA FROM BACKTRACE
  $trace[$la]['file'];
  $trace[$la]['line'];
  $trace[$la]['args'];
  $trace[$la]['function'];
  // DATA FROM BACKTRACE
  // LOOP ARGUMENTS ARRAY
  $ba = 0;
  $bb = count($trace[$la]['args']);
  while ($ba<$bb){
    $trace[$la]['args'][$ba] = "EDITING A REFERENCE/POINTER";
    $ba++;
  }
  unset($bb);
  unset($ba);
  // LOOP ARGUMENTS ARRAY
  $la++;
}
unset($lb);
unset($la);
// LOOP BACKTRACE
?>

It should be noted that if an internal php function such as call_user_func in the backtrace, the 'file' and 'line' entries will not be set.
Most debug tracers will use these entries. You should place a check to see if the key exists in the array before using this function. Otherwise notices will be generated.
<?php
$arrTrace = debug_backtrace();
foreach ($arrTrace as $arr)
{
  if (!isset ($arr['file']))
  {
    $arr['file'] = '[PHP Kernel]';
  }
  if (!isset ($arr['line']))
  {
    $arr['line'] = '';
  }
  // Do something
}
?>

I find it useful to know if a function is being called. in Java for instance you usually print a line with the functionname and arguments in the beginning of the function. I wanted to achieve the same thing in php thus i wrote the following class:
<?php
class Debug 
{
  private static $calls;
  public static function log($message = null)
  {
    if(!is_array(self::$calls))
      self::$calls = array();
    $call = debug_backtrace(false);
    $call = (isset($call[1]))?$call[1]:$call[0];
    $call['message'] = $message;
    array_push(self::$calls, $call);
  }
}
?>
include this class before anything else
usage: Debug::log($message); at the beginning of your function.
write yourself a nice printout of the data;

Surprisingly, no one has described one of the best uses of this: dumping a variable and showing the location. When debugging, especially a big and unfamiliar system, it's a pain remembering where I added those var dumps. Also, this way there is a separator between multiple dump calls.
<?php
function dump( $var ) {
  $result = var_export( $var, true );
  $loc = whereCalled();
  return "\n<pre>Dump: $loc\n$result</pre>";
}
function whereCalled( $level = 1 ) {
  $trace = debug_backtrace();
  $file  = $trace[$level]['file'];
  $line  = $trace[$level]['line'];
  $object = $trace[$level]['object'];
  if (is_object($object)) { $object = get_class($object); }
  return "Where called: line $line of $object \n(in $file)";
}
?>
In addition, calling 'whereCalled()' from any function will quickly identify locations that are doing something unexpected (e.g., updating a property at the wrong time). I'm new to PHP, but have used the equivalent in Perl for years.

I use this simple but effective function so i can see which method in the child class called the current method (in the parent class).
<?php
function get_caller_method()
{
  $traces = debug_backtrace();
  if (isset($traces[2]))
  {
    return $traces[2]['function'];
  }
  return null;
}
?>

Everybody seems to have their favorite use. I substitute this function for die(). It gives a message 
to the user and emails me a PrettyPrint of what went wrong. $info is set by me, 
and it does a special check in the database object.
<?php
// var_format
function var_format($v) // pretty-print var_export
{
  return (str_replace(array("\n"," ","array"),
array("<br>","&nbsp;","&nbsp;<i>array</i>"),
var_export($v,true))."<br>");
}
function myDie($info) 
{
  $mysqlerr=strpos($info,"ERROR=You have an error in your SQL syntax");
  if($mysqlerr>0)$info=substr($info,0,$mysqlerr)." mySql format error";
  $out="<br>MSG='$info'<br>".var_format($_REQUEST)."<br>";
  $bt=debug_backtrace();
  $sp=0;
  $trace="";
  foreach($bt as $k=>$v)
  {
    extract($v);
    $file=substr($file,1+strrpos($file,"/"));
    if($file=="db.php")continue; // the db object
    $trace.=str_repeat("&nbsp;",++$sp); //spaces(++$sp);
    $trace.="file=$file, line=$line, function=$function<br>";    
  } 
  $out.="<br>".backTrace();
  if(substr($info,0,4)=="XXX ") // special errrors when db is inaccessible
  {
    $out=str_replace("<br>","\n",$out);
    $out=str_replace("&nbsp;"," ",$out);
    mail("me@example.com","Database Execution Error for user ".$REMOTE_ADDR,"$out");
    exit("Database Access Error. Please try again later.");
  }
  mail("me@example.com",'Error Monitor','Execution Error',$out);
  exit("DANG! An execution error in the program has been sent to the webmaster. 
If you don't get an email from him soon, please call him.");
}
?>
This produces an output like this
 file=badmode.php, line=5, function=backTrace
 file=login.php, line=209, function=require
  file=midScreen.php, line=264, function=require
  file=masterindex.php, line=161, function=require
   file=production2.php, line=121, function=require
   file=index.php, line=16, function=require

I wrote this function, in addition to jlim, for a nice NO-HTML output. 
Thee result has similarities to a Java-error. Hope you like it. 
(BTW, this function exits the script too, if debug_backtrace is displayed)
------------------------------
  function debug_bt()
  {
    if(!function_exists('debug_backtrace'))
    {
      echo 'function debug_backtrace does not exists'."\r\n";
      return;
    }
    //echo '<pre>';
    echo "\r\n".'----------------'."\r\n";
    echo 'Debug backtrace:'."\r\n";
    echo '----------------'."\r\n";
    foreach(debug_backtrace() as $t)
    {
      echo "\t" . '@ ';
      if(isset($t['file'])) echo basename($t['file']) . ':' . $t['line'];
      else
      {
        // if file was not set, I assumed the functioncall
        // was from PHP compiled source (ie XML-callbacks).
        echo '<PHP inner-code>';
      }
      echo ' -- ';
      if(isset($t['class'])) echo $t['class'] . $t['type'];
      echo $t['function'];
      if(isset($t['args']) && sizeof($t['args']) > 0) echo '(...)';
      else echo '()';
      echo "\r\n";
    }
    //echo '</pre>';
    exit;
     }

Here is my simple example:
Code printing variable of class which instatiates the printing class.
Well, I am sure you understand when looking at the code:
Print result is: jippii
<?php
class A {
    function something() {
        $s = debug_backtrace();
        
        $callingObject = $s[1]['object']; 
        $test = $callingObject->jip;
        print $test;
    }
}
class B {
   var $jip; 
   
    function execute() {
        $a = new A();
        $this->jip = "jippii"; 
        $a->something(); 
    }
}
$control = new B();
$control->execute();
?>

Here's a way to get the arguments for an upstream function in your stack (works with class methods, static methods and non-class methods):
<?php
/**
 * getArgs - find arguments of upstream method
 * can be called with, e.g. "funcname", "class::staticmethod", "class->instancemethod".
 */
function getArgs( $target, $subclass_ok = true ) {
  if( strpos( $target, "::" ) ) {
    list( $class, $target ) = explode( "::", $target, 2 );
    $type = "::";
  }
  else if( strpos( $target, "->" ) ) {
    list( $class, $target ) = explode( "->", $target, 2 );
    $type = "->";
  }
  else {
    $type = NULL;
    $class = NULL;
  }
  $class and $class = new ReflectionClass( $class );
  foreach( debug_backtrace() as $obj ) {
    if( $obj['function'] == $target ) {
      if( $type and $obj['type'] == $type ) {
        $_cl = new ReflectionClass( $obj['class'] );
        if( $_cl->getName() == $class->getName() or ( $subclass_ok and $_cl->isSubclassOf( $class ) ) ) {
          return $obj['args'];
        }
        unset( $_cl );
      }
      else if( !$type ) {
        return $obj['args'];
      }
    }
  }
  return NULL;
}
?>
Some example usage:
<?php
class Foo {
  function test() {
    $args = getArgs( "Foo->base" );
    print( "the parameter 'v' to my call of base was: {$args[0]}\n" );
  }
  function base( $v ) {
    $this->test();
  }
}
$f = new Foo();
$f->base( 713 ); // will print.. ".. my call of base was: 713"
?>
Trust me, there are some reasons for why you might want to do this :)

<?
// useful and comfortable debug function
// it's show memory usage and time flow between calls, so we can quickly find a block of code that need optimisation...
// example result:
/*
debug example.php> initialize
debug example.php> code-lines: 39-41 time: 2.0002 mem: 19 KB
debug example.php> code-lines: 41-44 time: 0.0000 mem: 19 KB
debug example.php> code-lines: 44-51 time: 0.6343 mem: 9117 KB
debug example.php> code-lines: 51-53 time: 0.1003 mem: 9117 KB
debug example.php> code-lines: 53-55 time: 0.0595 mem: 49 KB
 */
function debug()
{
  static $start_time = NULL;
  static $start_code_line = 0;
  $call_info = array_shift( debug_backtrace() );
  $code_line = $call_info['line'];
  $file = array_pop( explode('/', $call_info['file']));
  if( $start_time === NULL )
  {
    print "debug ".$file."> initialize\n";
    $start_time = time() + microtime();
    $start_code_line = $code_line;
    return 0;
  }
  printf("debug %s> code-lines: %d-%d time: %.4f mem: %d KB\n", $file, $start_code_line, $code_line, (time() + microtime() - $start_time), ceil( memory_get_usage()/1024));
  $start_time = time() + microtime();
  $start_code_line = $code_line;
}
////////////////////////////////////////////////
// example:
debug();
sleep(2);
debug();
// soft-code...
$a = 3 + 5;
debug();
// hard-code
for( $i=0; $i<100000; $i++)
{
  $dummy['alamakota'.$i] = 'alamakota'.$i;
}
debug();
usleep(100000);
debug();
unset($dummy);
debug();
?>

I've started creating an external debug server for PHP. A PHP app require_once's a TADebugger(), which communicates with the debug sever. Find the OS X universal binary here [PHP source sample included]:
  http://www.turingart.com/downloads/phpDebugger.zip
Currently, TADebugger allows to post these properties back to the debug server:
- Call backtraces
- String messages
- Source files, which were referenced by a backtrace call
Note, that the binary is a early version.

A simple python-like backtrace. Note that I don't recurse into arrays if they are passed as arguments to functions.
function backtrace()
{
  $bt = debug_backtrace();
  
  echo("<br /><br />Backtrace (most recent call last):<br /><br />\n");  
  for($i = 0; $i <= count($bt) - 1; $i++)
  {
    if(!isset($bt[$i]["file"]))
      echo("[PHP core called function]<br />");
    else
      echo("File: ".$bt[$i]["file"]."<br />");
    
    if(isset($bt[$i]["line"]))
      echo("&nbsp;&nbsp;&nbsp;&nbsp;line ".$bt[$i]["line"]."<br />");
    echo("&nbsp;&nbsp;&nbsp;&nbsp;function called: ".$bt[$i]["function"]);
    
    if($bt[$i]["args"])
    {
      echo("<br />&nbsp;&nbsp;&nbsp;&nbsp;args: ");
      for($j = 0; $j <= count($bt[$i]["args"]) - 1; $j++)
      {
        if(is_array($bt[$i]["args"][$j]))
        {
          print_r($bt[$i]["args"][$j]);
        }
        else
          echo($bt[$i]["args"][$j]);  
              
        if($j != count($bt[$i]["args"]) - 1)
          echo(", ");
      }
    }
    echo("<br /><br />");
  }
}

Hi, I got tired of using a trace( $message, __FILE__, __LINE__ ) function I made. It forced me to include the file and line params (since php doesn't have macros) so I decided to make an alternative.
Simply call this new version using trace( 'my message' ); and it prints out a stack trace in a clearer way than the one stored in the debug_backtrace() array. It handles traces from outside of functions, traces in nested functions, and traces in included files, and also displays the function in a way that can be pasted right back into your php code for faster testing!
NOTE - be sure to save your files with the correct line endings for the line numbers to work correctly, which for Mac OS X is unix. You can get to this option in the popup menu in the toolbar at the top of each window in BBEdit.
<?php
function  print_var( $var )
{
  if( is_string( $var ) )
    return( '"'.str_replace( array("\x00", "\x0a", "\x0d", "\x1a", "\x09"), array('\0', '\n', '\r', '\Z', '\t'), $var ).'"' );
  else if( is_bool( $var ) )
  {
    if( $var )
      return( 'true' );
    else
      return( 'false' );
  }
  else if( is_array( $var ) )
  {
    $result = 'array( ';
    $comma = '';
    foreach( $var as $key => $val )
    {
      $result .= $comma.print_var( $key ).' => '.print_var( $val );
      $comma = ', ';
    }
    $result .= ' )';
    return( $result );
  }
  
  return( var_export( $var, true ) );  // anything else, just let php try to print it
}
function  trace( $msg )
{
  echo "<pre>\n";
  
  //var_export( debug_backtrace() ); echo "</pre>\n"; return;  // this line shows what is going on underneath
  
  $trace = array_reverse( debug_backtrace() );
  $indent = '';
  $func = '';
  
  echo $msg."\n";
  
  foreach( $trace as $val)
  {
    echo $indent.$val['file'].' on line '.$val['line'];
    
    if( $func ) echo ' in function '.$func;
    
    if( $val['function'] == 'include' ||
      $val['function'] == 'require' ||
      $val['function'] == 'include_once' ||
      $val['function'] == 'require_once' )
      $func = '';
    else
    {
      $func = $val['function'].'(';
      
      if( isset( $val['args'][0] ) )
      {
        $func .= ' ';
        $comma = '';
        foreach( $val['args'] as $val )
        {
          $func .= $comma.print_var( $val );
          $comma = ', ';
        }
        $func .= ' ';
      }
      
      $func .= ')';
    }
    
    echo "\n";
    
    $indent .= "\t";
  }
  
  echo "</pre>\n";
}
trace( 'error outside function' );
function  test( $param1, $param2, $param3, $param4 )
{
  trace( 'error in test()' );
}
test( 1.1, "param2\n", array( 1 => "a\n", "b\n" => 2 ), false );
?>

Surprizingly, debug_backtrace() cannot aquire arguments from the function that is used as the second or later argument of a function.
<?php
function a($p) {
  $backtrace = debug_backtrace();
  
  if (isset($backtrace[0]['args']))
    var_export($backtrace[0]['args']);
  else
    echo "Cannot aquire arguments";
  echo "<br />";
  
  return $p;
}
function b($p1, $p2, $p3) {
  echo "$p1, $p2, $p3";
}
// This outputs:
//  array ( 0 => 'First a', )
//  Cannot aquire arguments
//  Cannot aquire arguments
//  First a, Second a, Third a
b(a("First a"), a("Second a"), a("Third a"));
?>

Pretty print the backtrace(). Functions are indented based on call value, and file is linked using file:// for convenience. 
Enjoy, John Lim
  function adodb_backtrace($print=true)
  {
    $s = '';
    if (PHPVERSION() >= 4.3) {
    
      $MAXSTRLEN = 64;
    
      $s = '<pre align=left>';
      $traceArr = debug_backtrace();
      array_shift($traceArr);
      $tabs = sizeof($traceArr)-1;
      foreach ($traceArr as $arr) {
        for ($i=0; $i < $tabs; $i++) $s .= ' &nbsp; ';
        $tabs -= 1;
        $s .= '<font face="Courier New,Courier">';
        if (isset($arr['class'])) $s .= $arr['class'].'.';
        foreach($arr['args'] as $v) {
          if (is_null($v)) $args[] = 'null';
          else if (is_array($v)) $args[] = 'Array['.sizeof($v).']';
          else if (is_object($v)) $args[] = 'Object:'.get_class($v);
          else if (is_bool($v)) $args[] = $v ? 'true' : 'false';
          else { 
            $v = (string) @$v;
            $str = htmlspecialchars(substr($v,0,$MAXSTRLEN));
            if (strlen($v) > $MAXSTRLEN) $str .= '...';
            $args[] = $str;
          }
        }
        
        $s .= $arr['function'].'('.implode(', ',$args).')';
        $s .= sprintf("</font><font color=#808080 size=-1> # line %4d,".
 " file: <a href=\"file:/%s\">%s</a></font>",
 $arr['line'],$arr['file'],$arr['file']);
        $s .= "\n";
      }  
      $s .= '</pre>';
      if ($print) print $s;
    }
    return $s;
  }

A function that i use for debug
I shortened variables name and i eliminated the spaces from second function in order fit in post :(
<?php
define("LFP", './lt.log');
function LogTrace($Argument, $lfn = LFP, $itw = ' ')
{
  error_log("=====\r", 3, $lfn); 
  error_log("[BEGIN BACKTRACE]\r", 3, $lfn); 
  $it = '';
  $Ts = array_reverse(debug_backtrace());
  foreach($Ts as $T)
    { 
    if($T['function'] != 'include' && $T['function'] != 'require' && $T['function'] != 'include_once' && $T['function'] != 'require_once')
    {
      $ft = $it . '<'. basename($T['file']) . '> on line ' . $T['line']; 
      if($T['function'] != 'LogTrace')
      {
        if(isset($T['class']))
          $ft .= ' in method ' . $T['class'] . $T['type'];
        else 
          $ft .= ' in function ';
        $ft .= $Trace['function'] . '(';
      }
      else
        $ft .= '(';
      if(isset($T['args'][0]))
      {
        if($T['function'] != 'LogTrace')
        {
          $ct = '';
          foreach($T['args'] as $A)
          {
            $ft .= $ct . LogVar($A, '', $it, $itw, 0);
            $ct = $it . $itw . ',';
          }
        }
        else
          $ft .= LogVar($T['args'][0], '', $it, $itw, 0);
      }
      $ft .= $it . ")\r";
      error_log($ft, 3, $lfn); 
      $it .= $itw;
    }      
  }
  error_log("[END BACKTRACE]\r", 3, $lfn);
}
function LogVar(&$Var, $vn, $pit, $itw, $nlvl, $m = '')
{
  if($nlvl>=16) return;
  if($nlvl==0){$tv=serialize($Var);$tv=unserialize($tv);}
  else $tv=&$Var; 
  $it=$pit.$itw;
  for($i=0; $i<$nlvl;$i++) $it.='.'.$itw;
  $o='';$nl="\n";
  if(is_array($tv))
  {
    if(strlen($vn)>0) $o.=$it.$m.'<array> $'.$vn.' = (';
    else $o.="\r".$it.$m.'<array> = (';
    $o.= $nl;$AK=array_keys($tv);
    foreach($AK as $AN) {$AV=&$tv[$AN];$o.=LogVar($AV,$AN,$pit,$itw,$nlvl+1);}
    $o.=$it.')'.$nl;
  }
  else if(is_string($tv))
  {
    if(strlen($vn)>0)$o.=$it.$m.'<string> $'.$vn.' = ';
    else $o.=' '.$m.'<string> = ';
    if($tv===null) $o.='NULL';
    else $o.='"'.$tv.'"';
    $o.=$nl;
  }
  else if(is_bool($tv))
  {
    if(strlen($vn) > 0) $o.=$it.$m.'<boolean> $'.$vn.' = ';
    else $o.=' '.$m.'<boolean> = ';
    if($tv===true) $o.='TRUE';
    else $o.='FALSE';
    $o.=$nl;
  }
  else if(is_object($tv))
  {
    if(strlen($vn)>0)
    {
      $o.=$pit.$itw;
      for($i=0;$i<$nlvl;$i++) $o.='.'.$itw;
      $o.=$m.'<'.get_class($tv).'::$'.$vn.'> = {'.$nl;
    }
    else $o.=' '.$m.'<'.get_class($tv).'::> = {'.$nl;
    $R=new ReflectionClass($tv);
    $o.=$it.'.'.$itw.'Class methods {'.$nl;
    $CM=$R->getMethods();
    foreach($CM as $MN => $MV)
    {
      $o.=$it.'.'.$itw.'.'.$itw.implode(' ',Reflection::getModifierNames($MV->getModifiers())).' '.$MV->getName().'(';
      $MP=$MV->getParameters(); $ct='';
      foreach($MP as $MPN => $MPV)
      {
        $o.=$ct; $o.=$MPV->isOptional()?'[':'';
        if($MPV->isArray()) $o.='<array> ';
        else if($MPV->getClass()!==null) $o.='<'.$MPV->getClass() >getName().'::> ';
        $o.=$MPV->isPassedByReference()?'&':''; $o.='$'.$MPV->getName();
        if($MPV->isDefaultValueAvailable())
         {
          if($MPV->getDefaultValue()===null) $o.=' = NULL';
          else if($MPV->getDefaultValue()===true) $o.=' = TRUE';
          else if($MPV->getDefaultValue()===false) $o.=' = FALSE';  
          else $o.=' = '.$MPV->getDefaultValue();  
        }
        $o.=$MPV->isOptional()?']':''; $ct=', ';
      }
      $o.=')'.$nl;
    }
    $o.=$it.'.'.$itw.'}'.$nl; $o.=$it.'.'.$itw.'Class properties {'.$nl;
    $CV=$R->getProperties();
    foreach($CV as $CN => $CV)
    {
      $M=implode(' ',Reflection::getModifierNames($CV->getModifiers())).' ';
      $CV->setAccessible(true); 
      $o.=LogVar($CV->getValue($tv),$CV->getName(),$pit,$itw,$nlvl+2,$M);
    }
    $o.=$it.'.'.$itw.'}'.$nl; $o.=$it.'.'.$itw.'Object variables {'.$nl;
     $OVs=get_object_vars($tv);  
    foreach($OVs as $ON => $OV) $o.=LogVar($OV,$ON,$pit,$itw,$nlvl+2);
    $o.=$it.'.'.$itw.'}'.$nl; $o.=$pit.$itw;
    for($i=0;$i<$nlvl;$i++)  $o.='.'.$itw;
    $o.='}'.$nl;
  }
  else
  {
    if(strlen($vn)>0) $o.=$it.$m.'<'.gettype($tv).'> $'.$vn.' = '.$tv;
    else $o.=' '.$m.'<'.gettype($tv).'> = '.$tv;
    $o.=$nl;
  }     
  return $o;  
}
//test
date_default_timezone_set('Europe/Bucharest');
$date = new DateTime('2010-01-28');
LogTrace($date); 
?>

An easy function to pull all details of the debug backtrace:
<?php
function getDebugBacktrace($NL = "<BR>") {
  $dbgTrace = debug_backtrace();
  $dbgMsg .= $NL."Debug backtrace begin:$NL";
  foreach($dbgTrace as $dbgIndex => $dbgInfo) {
    $dbgMsg .= "\t at $dbgIndex ".$dbgInfo['file']." (line {$dbgInfo['line']}) -> {$dbgInfo['function']}(".join(",",$dbgInfo['args'])")$NL";
  }
  $dbgMsg .= "Debug backtrace end".$NL;
  return $dbgMsg;
}
?>
Then you can call it anywhere you want to get a string with the debug backtrace in readable format (i.e. your error handling function)
<?php
$backtrace = getDebugBacktrace();
echo "Fatal error! Cannot connect to database!";
echo $backtrace;
?>
If you're running on command line, you might want to replace the line split. You can do that thru the function argument:
<?php
$backtrace = getDebugBacktrace("\n");
echo "Error! Server is running out of foos! Dumping error backtrace";
echo $backtrace;
?>
Hope that helps,
Aryel

ATTN: jlim#natsoft.com.my
Great function, but you have a few bugs.
At the line: 
foreach($arr['args'] as $v)
Change it to:
$args = array();
if(!empty($arr['args'])) foreach($arr['args'] as $v)
And since line & file are not present in the array if calling from the error handler,
$Line = (isset($arr['line'])? $arr['line'] : "unknown");
$File = (isset($arr['file'])? $arr['file'] : "unknown");
and substitute accordingly.
Here's my version of it, alas with different formatting:
----------------------------------------
function DBG_GetBacktrace()
{
  $s = '';
  $MAXSTRLEN = 64;
  
  $s = '<pre align=left>';
  $traceArr = debug_backtrace();
  array_shift($traceArr);
  $tabs = sizeof($traceArr)-1;
  foreach($traceArr as $arr)
  {
    for ($i=0; $i < $tabs; $i++) $s .= ' &nbsp; ';
    $tabs -= 1;
    $s .= '<font face="Courier New,Courier">';
    if (isset($arr['class'])) $s .= $arr['class'].'.';
    $args = array();
    if(!empty($arr['args'])) foreach($arr['args'] as $v)
    {
      if (is_null($v)) $args[] = 'null';
      else if (is_array($v)) $args[] = 'Array['.sizeof($v).']';
      else if (is_object($v)) $args[] = 'Object:'.get_class($v);
      else if (is_bool($v)) $args[] = $v ? 'true' : 'false';
      else
      { 
        $v = (string) @$v;
        $str = htmlspecialchars(substr($v,0,$MAXSTRLEN));
        if (strlen($v) > $MAXSTRLEN) $str .= '...';
        $args[] = "\"".$str."\"";
      }
    }
    $s .= $arr['function'].'('.implode(', ',$args).')</font>';
    $Line = (isset($arr['line'])? $arr['line'] : "unknown");
    $File = (isset($arr['file'])? $arr['file'] : "unknown");
    $s .= sprintf("<font color=#808080 size=-1> # line %4d, file: <a href=\"file:/%s\">%s</a></font>",
      $Line, $File, $File);
    $s .= "\n";
  }  
  $s .= '</pre>';
  return $s;
}