php man page for uasort

UASORT(3)								 1								 UASORT(3)

uasort - Sort an array with a user-defined comparison function and maintain index association

SYNOPSIS
       bool uasort (array  &$array, callable  $value_compare_func)

DESCRIPTION
	This  function sorts an array such that array indices maintain their correlation with the array elements they are associated with, using a
       user-defined comparison function.

	This is used mainly when sorting associative arrays where the actual element order is significant.

       Note

	       If two members compare as equal, their relative order in the sorted array is undefined.

PARAMETERS
	      o $array
		- The input array.

	      o $value_compare_func
		- See usort(3) and uksort(3) for examples of user-defined comparison functions.

RETURN VALUES
	Returns TRUE on success or FALSE on failure.

EXAMPLES
       Example #1

	      Basic uasort(3) example

	      <?php
	      // Comparison function
	      function cmp($a, $b) {
		  if ($a == $b) {
		      return 0;
		  }
		  return ($a < $b) ? -1 : 1;
	      }

	      // Array to be sorted
	      $array = array('a' => 4, 'b' => 8, 'c' => -1, 'd' => -9, 'e' => 2, 'f' => 5, 'g' => 3, 'h' => -4);
	      print_r($array);

	      // Sort and print the resulting array
	      uasort($array, 'cmp');
	      print_r($array);
	      ?>

	      The above example will output:

	      Array
	      (
		  [a] => 4
		  [b] => 8
		  [c] => -1
		  [d] => -9
		  [e] => 2
		  [f] => 5
		  [g] => 3
		  [h] => -4
	      )
	      Array
	      (
		  [d] => -9
		  [h] => -4
		  [c] => -1
		  [e] => 2
		  [g] => 3
		  [a] => 4
		  [f] => 5
		  [b] => 8
	      )

SEE ALSO
       usort(3), The comparison of array sorting functions.

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