class_uses()

(PHP 5 >= 5.4.0, PHP 7)

Return the traits used by the given class

说明

class_uses(mixed $class[,bool $autoload= TRUE]): array

This function returns an array with the names of the traits that the given$classuses. This does however not include any traits used by a parent class.

参数

$class: An object(class instance)or a string(class name).
$autoload: Whether to allow this function to load the class automatically through the __autoload() magic method.

返回值

An array on success, or FALSE on error.

范例

class_uses() example

<?php
trait foo { }
class bar {
  use foo;
}
print_r(class_uses(new bar));
print_r(class_uses('bar'));
function __autoload($class_name) {
   require_once $class_name . '.php';
}
// use __autoload to load the 'not_loaded' class
print_r(class_uses('not_loaded', true));
?>

以上例程的输出类似于：

Array
(
    [foo] => foo
)
Array
(
    [foo] => foo
)
Array
(
    [trait_of_not_loaded] => trait_of_not_loaded
)

参见

class_parents()返回指定类的父类。
get_declared_traits()返回所有已定义的 traits 的数组

To get ALL traits including those used by parent classes and other traits, use this function:
<?php
function class_uses_deep($class, $autoload = true) {
  $traits = [];
  do {
    $traits = array_merge(class_uses($class, $autoload), $traits);
  } while($class = get_parent_class($class));
  foreach ($traits as $trait => $same) {
    $traits = array_merge(class_uses($trait, $autoload), $traits);
  }
  return array_unique($traits);
}
?>

If the class does not exist, you will get a warning, even if $autoload == false; I.e., if the class is not found, setting $autoload to false is not sufficient to silence the warning.
This is different from class_exists ($class_name, $autoload = true), which doesn't generate a warning in either case.

A slighly modified version from Stealz that also checks all the "parent" traits used by the traits:
<?php
public static function class_uses_deep($class, $autoload = true)
  {
    $traits = [];
    // Get traits of all parent classes
    do {
      $traits = array_merge(class_uses($class, $autoload), $traits);
    } while ($class = get_parent_class($class));
    // Get traits of all parent traits
    $traitsToSearch = $traits;
    while (!empty($traitsToSearch)) {
      $newTraits = class_uses(array_pop($traitsToSearch), $autoload);
      $traits = array_merge($newTraits, $traits);
      $traitsToSearch = array_merge($newTraits, $traitsToSearch);
    };
    foreach ($traits as $trait => $same) {
      $traits = array_merge(class_uses($trait, $autoload), $traits);
    }
    return array_unique($traits);
  }
?>

I have improved on ulf's improvement of stealz' code. I'm pretty sure the last "foreach" adds nothing, so I've removed it, as well as adding a check for string class names (as opposed to objects) to prevent the warning if the class is not found:
<?php
function class_uses_deep($class, $autoload = true) {
 $traits = [];
 // Get all the traits of $class and its parent classes
 do {
  $class_name = is_object($class)? get_class($class): $class;
  if (class_exists($class_name, $autoload)) {
   $traits = array_merge(class_uses($class, $autoload), $traits);
  }
 } while ($class = get_parent_class($class));
 // Get traits of all parent traits
 $traits_to_search = $traits;
 while (!empty($traits_to_search)) {
  $new_traits = class_uses(array_pop($traits_to_search), $autoload);
  $traits = array_merge($new_traits, $traits);
  $traits_to_search = array_merge($new_traits, $traits_to_search);
 };
 return array_unique($traits);
}

FYI: It is not explicitly stated, but if you run this function against a class that does not use any traits it will return an empty array.
<?php
class iDontUseTraits {
}
class_uses('iDontUseTraits'); // Returns empty array
?>