PHP comes with a number of built-in functions that are used to sort arrays in an easier way. Here, we are going to discuss a new function usort(). The usort() function in PHP sorts a given array by using a user-defined comparison function. This function is useful in case if we want to sort the array in a new manner. This function assigns new integral keys starting from zero to the elements present in the array and the old keys are lost.
Syntax:
boolean usort( $array, "function_name");
Parameters: This function accepts two parameters as shown in the above syntax and are described below:
- $array: This parameter specifies the array which u want to sort.
- function_name : This parameter specifies the name of a user-defined function which compares the values and sort the array specified by the parameter $array. This function returns an integer value based on the following conditions. If two arguments are equal, then it returns 0, If first argument is greater than second, it returns 1 and if first argument is smaller than second, it returns -1.
Return Value: This function returns the boolean type of value. It returns TRUE in case of success and FALSE in case of failure.
Below program illustrate the usort() function in PHP:
<?php       // PHP program to illustrate usort() function       // This is the user-defined function used to compare     // values to sort the input array     function comparatorFunc( $x, $y)     {           // If $x is equal to $y it returns 0         if ($x== $y)             return 0;               // if x is less than y then it returns -1         // else it returns 1            if ($x < $y)             return -1;         else            return 1;     }           // Input array     $arr= array(2, 9, 1, 3, 5);       usort($arr, "comparatorFunc");           print_r($arr);   ?> |
Output:
Array
(
[0] => 1
[1] => 2
[2] => 3
[3] => 5
[4] => 9
)
Reference:
http://php.net/manual/en/function.usort.php
