PHP - Function usort()


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Syntax

usort ( $array, $cmp_function )

Definition and Usage

The usort() function sorts an array by a user defined comparison function. This function assigns new keys for the elements in the array. Existing keys will be removed.

Parameters

Parameter Description
array Required. Specifies an array.
cmp_function

Required. Useful defined function to compare values and to sort them.

The function must return -1, 0, or 1 for this method to work correctly. It should be written to accept two parameters to compare, and it should work something like this −

  • If a = b, return 0
  • If a > b, return 1
  • If a < b, return -1

Return Value

Returns TRUE on success or FALSE on failure.

Example

Try out following example −

<?php
   function cmp_function($a, $b)
   {
      if ($a == $b) return 0;
      return ($a > $b) ? -1 : 1;
   }
   
   $fruits = array("d"=>"lemon", "a"=>"orange", "b"=>"banana" );
   usort($fruits, "cmp_function");
   
   print_r($fruits);
?> 

This will produce the following result −

Array ( [0] => orange [1] => lemon [2] => banana )

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