trigger_error()

(PHP 4 >= 4.0.1, PHP 5, PHP 7)

产生一个用户级别的 error/warning/notice 信息

说明

trigger_error(string $error_msg[,int $error_type= E_USER_NOTICE]): bool

用于触发一个用户级别的错误条件，它能结合内置的错误处理器所关联，或者可以使用用户定义的函数作为新的错误处理程序(set_error_handler())。

该函数在你运行出现异常时，需要产生一个特定的响应时非常有用。

参数

$error_msg: 该 error 的特定错误信息，长度限制在了 1024 个字节。超过 1024 字节的字符都会被截断。
$error_type: 该 error 所特定的错误类型。仅 E_USER 系列常量对其有效，默认是E_USER_NOTICE。

返回值

如果指定了错误的$error_type会返回FALSE，正确则返回TRUE。

范例

Example #1trigger_error()示例

set_error_handler()可见到更多详细的例子。

<?php
if ($divisor == 0) {
    trigger_error("Cannot divide by zero", E_USER_ERROR);
}
?>

注释

Warning
在$error_msg里的HTML实体并不会被转义。如果错误消息要显示在浏览器里，需要对错误消息使用htmlentities()。

参见

error_reporting() 设置应该报告何种 PHP 错误
set_error_handler() 设置用户自定义的错误处理函数
restore_error_handler() 还原之前的错误处理函数
The错误级别常量

the idea is never to give out file names, line numbers, and cryptic codes to the user. Use trigger_error() after you used set_error_handler() to register your own callback function which either logs or emails the error codes to you, and echo a simple friendly message to the user.
And turn on a more verbose error handler function when you need to debug your scripts. In my init.php scripts I always have:
if (_DEBUG_) {
  set_error_handler ('debug_error_handler');
}
else {
  set_error_handler ('nice_error_handler');
}

trigger_error always reports the line and file that trigger_error was called on. Which isn't very useful.
eg:
main.php:
<?php
include('functions.php');
$x = 'test';
doFunction($x);
?>
functions.php:
<?php
function doFunction($var) {
if(is_numeric($var)) {
 /* do some stuff*/
} else {
 trigger_error('var must be numeric');
}
}
?>
will output "Notice: var must be numeric in functions.php on line 6"
whereas "Notice: var must be numeric in main.php on line 4" would be more useful
here's a function to do that:
<?php
function error($message, $level=E_USER_NOTICE) {
$caller = next(debug_backtrace());
trigger_error($message.' in <strong>'.$caller['function'].'</strong> called from <strong>'.$caller['file'].'</strong> on line <strong>'.$caller['line'].'</strong>'."\n<br />error handler", $level);
}
?>
So now in our example:
main.php:
<?php
include('functions.php');
$x = 'test';
doFunction($x);
?>
functions.php:
<?php
function doFunction($var) {
  if(is_numeric($var)) {
     /* do some stuff*/
  } else {
     error('var must be numeric');
  }
}
function error($message, $level=E_USER_NOTICE) {
  $caller = next(debug_backtrace());
  trigger_error($message.' in <strong>'.$caller['function'].'</strong> called from <strong>'.$caller['file'].'</strong> on line <strong>'.$caller['line'].'</strong>'."\n<br />error handler", $level);
}
?>
now outputs:
"Notice: var must be numeric in doFunction called from main.php on line 4"

i recently began using a custom error handling class. the biggest problem is that, with call time pass by reference deprecated, you can't manipulate the error handler class after assigning at as the error handler (and it appears not to be returned by the set_error_handler method as the old error handler). my goal was to be able to store up all my non-fatal errors and print them at the end of script execution. that way i can use 'trigger_error' (which i actually have wrapped in a static method ErrorHandler::throwException for portability purposes... which is a pain because it always has the same line number information!!) for all kinds of errors, including user input erros. so when i check a user's password, for instance i would trigger a warning that said 'incorrect password'. of course i would only want this to print out the error once the script had completed. 
so in my error handler class i have the following in the constructor:
function ErrorHandler()
{
  $this->error_messages = array();
  error_reporting (E_ALL);
  set_error_handler(array($this,"assignError"));
}
and my assignError method:
//accept the required arguments
function assignError($errno, $errstr, $errfile, $errline)
{
  //get the error string
  $error_message = $errstr;
//if in debug mode, add line number and file info
 if(ErrorHandler::DEBUG())
 $error_message .= "<br>".basename($errfile).",line: ".$errline;
      switch ($errno)
      {
        //if the error was fatal, then add the error
        //display an error page and exit
        case ErrorHandler::FATAL():
          $this->setType('Fatal');
          $this->addError($error_message);
          Display::errorPage($this->errorMessages());
          exit(1);
        break;
        //if it was an error message, add a message of
        //type error
        case ErrorHandler::ERROR():
          $this->setType('Error');
          $this->addError($error_message);
        break;
        //if it was a warning, add a message of type
        //warning
        case ErrorHandler::WARNING():
          $this->setType('Warning');
          $this->addError($error_message);
        break;
        //if it was some other code then display all
        //the error messages that were added
        default:
          Display::errorRows($this->errorMessages());
        break;
      }
      //return a value so that the script will continue
      //execution
      return 1;
}
the key part there is the 'default' behaviour. i found that if i call trigger_error with anything other than E_USER_ERROR, E_USER_WARNING or E_USER_NOTICE, then error code '2' is passed to the handler method. so when it is time to print all my non-fatal errors, like 'password and confirm password don't match' or something, i call ErrorHandler::printAllErrors()
    function printAllErrors()
    {
      trigger_error("",2);
    }
which leads to the default behaviour in my switch statement in the assignError method above. the only problem with this is that the weird bug 'Problem with method call' that occurs with some static method calls (that one person on the bug lists said was fixed and another said wouldn't be fixed until version 5) also produces error code 2!! i have just taken to suppressing these errors with @, because despite the alledged problem with the method call, the script still seems to execute fine.
iain.

If error_type is E_USER_ERROR then trigger_error throw FATAL ERROR and script stopped after this line.
<?php
$msg = 'This is the test message for echo';
trigger_error('Error message', E_USER_ERROR); // Script stopped after this line...
echo $msg; // This line does not appear...
?>

Beware, trigger_error() is absolutely useless for transporting your own function's error messages in $php_errormsg:
ini_set('track_errors', TRUE);
function x() { trigger_error('MY ERROR'); }
@x();
echo "Error 1: \\"$php_errormsg\\"\\n";
@file_get_contents('/nonexisting');
echo "Error 2: \\"$php_errormsg\\"\\n";
This outputs:
Error 1: ""
Error 2: "failed to open stream: No such file or directory"
This behaviour is consistent with the description of $php_errormsg, which says that the variable will only be available within the scope in which the error occurred. The problem can be worked around with a custom error handler like the one below. However, I'm undecided whether changing the language in this way is good:
function errHandler($errno, $errstr, $errfile, $errline) {
 global $php_errormsg; $php_errormsg = $errstr;
}
set_error_handler('errHandler');

Some might think that trigger_error is like a throw() or an err.raise construction, and @ works like catch(){} one - in fact it's NOT.
function badgirl(){
  trigger_error("shame on me",E_USER_ERROR);
  return true;
}
$sheis = @badgirl();
echo "You will never see this line - @ only supress message, not a control flow";

For those of you wanting one (or more) lines of context on your call to trigger_error, I offer this. Would be nice to use \n to get a proper stack trace, but it seems trigger_error escapes it; therefore, I use a comma.
<?php
/**
 * Behaves like trigger_error, but appends part of a stack trace to the error
 * message. This allows you to see where trigger_error was called from, instead
 * of just seeing the file and line number of the call to trigger_error.
 *
 * @param  error_msg  The designated error message for this error
 * @param  error_type The designated error type for this error (E_USER_*)
 * @param  context   Number of stack frames to append, defaults to 1
 * @return FALSE if wrong error_type is specified, TRUE otherwise
 */
function trigger_error_with_context($error_msg, $error_type, $context = 1) {
  $stack = debug_backtrace();
  for ($i = 0; $i < $context; $i++)
  {
    if (false === ($frame = next($stack))
      break;
    $error_msg .= ", from " . $frame['function'] . ':' . $frame['file'] . ' line ' . $frame['line'];
  }
  return trigger_error($error_msg, $error_type);
}
?>

For those of you looking to use your own file or line number in the error (possibly using debug_backtrace()) instead of the ones created by trigger_error(), here is a solution:
Create a custom function to handle E_USER_ERRORs that simply outputs the error type and message, while excluding the line number and file trigger_error() reports. You may also configure it to handle user warnings and notices if necessary (I did in the example below).
<?php
function error_handler($level, $message, $file, $line, $context) {
  //Handle user errors, warnings, and notices ourself
  if($level === E_USER_ERROR || $level === E_USER_WARNING || $level === E_USER_NOTICE) {
    echo '<strong>Error:</strong> '.$message;
    return(true); //And prevent the PHP error handler from continuing
  }
  return(false); //Otherwise, use PHP's error handler
}
function trigger_my_error($message, $level) {
  //Get the caller of the calling function and details about it
  $callee = next(debug_backtrace());
  //Trigger appropriate error
  trigger_error($message.' in <strong>'.$callee['file'].'</strong> on line <strong>'.$callee['line'].'</strong>', $level);
}
//Use our custom handler
set_error_handler('error_handler');
//-------------------------------
//Demo usage:
//-------------------------------
function abc($str) {
  if(!is_string($str)) {
    trigger_my_error('abc() expects parameter 1 to be a string', E_USER_ERROR);
  }
}
abc('Hello world!'); //Works
abc(18); //Error: abc() expects parameter 1 to be a string in [FILE].php on line 31
?>
This is a pretty simple concept and I'm sure most of you know this, but for those that don't, let it serve as a good example!

It actually turns out - at least on PHP 5.2.6 on XAMPP (Windows) that for the custom error handler, you will need to set $errorType as the first parameter, and only the second parameter as $message, i.e. in reverse order compared to how the manual states it now.

Trigger error does not trim 1024+ chars length messages if you use your own error handler

I am not so familiar with this but I think you can reach some of the functionality of try..catch with this function. I would disagree or correct the previous note. The @ is not the catch, it sets the error_reporting to 0 tempolary but with set_error_handler you can try to imitate some behavior like catch.
I've just made this to try if it possible, I never tried in projects but I think could work in php 4. Actually if you want to have the Trace of the error you need to use php4.3+.
Maybe not many of you will create new scripts in php4 and try to have some features from php5 but in some cases (extending older projects) this could be better error handling.
If this is a wrong approach, waiting for comments, if its not, use it!
<?
function catch($errno, $errstr, $errfile, $errline){
  $GLOBALS['throw'] = $errstr;
  $GLOBALS['throw_info'] = array(
    'Message'=>$errstr
    ,'Code'=>$errno
    ,'Line'=>$errline
    ,'File'=>$errfile
    ,'Trace'=>debug_backtrace()
  );
  
}
set_error_handler('catch');
function badgirl(){
  if(true){ //error occure
    trigger_error("BadGirlWithError",E_USER_NOTICE); // as throw with notice
    return; // ...because trigger_error does not stop the function
  }else{
    return true;
  }
}
// Try 
$GLOBALS['throw'] = null; // ...try...
$sheis = badgirl(); //could be @badgirl, display_errors is something else, this just the handling
// ..try
if($GLOBALS['throw']){ // This actually catch re-throws too...
  switch($GLOBALS['throw']){ // Catch
    case 'GoodGirlException':
      die('No bad girl today!');
    break;
    case 'BadGirlWithError':
      die('Bad girl has some error');
    break;
    default:
      return; // or you can make another trigger_error and re-throw another 'exception' or some other action
  }
}
echo "You will never see this line - @ only supress message, not a control flow";
echo "Wrong! You could see this:)";
?>
.mano

This one took me some time ...
When you use trigger_error with your own error handler, the class instances are destroyed (don't know how to say it better, I am not an expert).
So, if you try to call a class function from within the error handler function, you will get 'Call to a member function on a non-object' error, even if this function works perfectly in the rest of your script.
Solution : re-use the xxx = new yyy to re-create the instance in the beginning of your error handler ... and then you can call the class functions you want !

We wanted to be able to pass an SQL query to the error handler on our site so we could monitor SQL problems, you cant do this through normal methods so we came up with this bridge script that 100% works
<?php
function myErrorHandler($errno, $errstr, $errfile, $errline){
  switch ($errno) {
  case E_USER_ERROR:
    if ($errstr == "(SQL)"){
      // handling an sql error
      echo "<b>SQL Error</b> [$errno] " . SQLMESSAGE . "<br />\n";
      echo "Query : " . SQLQUERY . "<br />\n";
      echo "On line " . SQLERRORLINE . " in file " . SQLERRORFILE . " ";
      echo ", PHP " . PHP_VERSION . " (" . PHP_OS . ")<br />\n";
      echo "Aborting...<br />\n";
    } else {
      echo "<b>My ERROR</b> [$errno] $errstr<br />\n";
      echo " Fatal error on line $errline in file $errfile";
      echo ", PHP " . PHP_VERSION . " (" . PHP_OS . ")<br />\n";
      echo "Aborting...<br />\n";
    }
    exit(1);
    break;
  case E_USER_WARNING:
  case E_USER_NOTICE:
  }
  /* Don't execute PHP internal error handler */
  return true;
}
// function to test the error handling
function sqlerrorhandler($ERROR, $QUERY, $PHPFILE, $LINE){
  define("SQLQUERY", $QUERY);
  define("SQLMESSAGE", $ERROR);
  define("SQLERRORLINE", $LINE);
  define("SQLERRORFILE", $PHPFILE);
  trigger_error("(SQL)", E_USER_ERROR);
}
set_error_handler("myErrorHandler");
// trigger an sql error
$query = "SELECT * FROM tbl LIMIT 1";
$sql = @mysql_query($query)
  or sqlerrorhandler("(".mysql_errno().") ".mysql_error(), $query, $_SERVER['PHP_SELF'], __LINE__);
  
?>

Well this is a good way on debuging your php scripts, but i wouldn't feel
too comfortable by giving out my web servers structure.
Notice that what helps you finding and isolating errors in your php helps also a potential attacker.
Or maybe i am just paranoid, but its worth mention it.

You should be using set_error_handler (possibly in conjuction with error_log and/or trigger_error) if you want FILE and LINE number information.
You don't need macros for this.