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PHP usort() Function

❮ PHP Array Reference


Sort the elements of an array by values using a user-defined comparison function:

function my_sort($a, $b) {
  if ($a == $b) return 0;
  return ($a < $b) ? -1 : 1;

$a = array(4, 2, 8, 6);
usort($a, "my_sort");

foreach($a as $key => $value) {
  echo "[" . $key . "] => " . $value;
  echo "<br>";
Try it Yourself »

Definition and Usage

The usort() function sorts an array by values using a user-defined comparison function.

Tip: Use the uksort() function to sort an array by keys using a user-defined comparison function.

Tip: Use the uasort() function to sort an array by values (and maintain the index association) using a user-defined comparison function. 


usort(array, callback)

Parameter Values

Parameter Description
array Required. Specifies the array to sort
callback Required. A comparison function. Must return an integer <, =, or > than 0 if the first argument is <, =, or > than the second argument

Technical Details

Return Value: Always returns TRUE
PHP Version: 4+
PHP Changelog: PHP 8.2.0: Now returns TRUE (previously it returned bool)
PHP 8.0.0: If callback expects a parameter to be passed by reference, it will now return an E_WARNING

❮ PHP Array Reference