PHP usort() Function

PHP usort() Function

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

Syntax

usort ( array &$array , callable $value_compare_func )

array(required)- This parameter represents the input array.

value_compare_func(required)- This parameter represents a string that describe a callable comparison function. The comparison function must return an integer <, =, or > than 0 if the first argument is <, =, or > than the second argument.

Return

This function returns a Boolean value TRUE on success or FALSE on failure.

Example 1

 "green", "b" => "brown", "i" => "indigo", "red");
 echo("Input Array: \n");
 print_r($array);
 //sorting the array by values using a "strcasecmp" comparison function
 usort($array, "strcasecmp");
 echo("Sorted Array: \n");
 print_r($array);
 ?> 

Output

Input Array: 
 Array
 (
     [g] => green
     [b] => brown
     [i] => indigo
     [0] => red
 )
 Sorted Array:  
 Array
 (
     [0] => brown
     [1] => green
     [2] => indigo
     [3] => red
 ) 

Example 2

$b)?1:-1; 
 }
 $array1=array("1"=>"red","2"=>"green","3"=>"blue");
 echo("Original Array: \n");
 print_r($array1);
 // comparing the keys and values with additional index check 
 usort ($array1,"myfunction");
 echo("\nSorted Array: \n");
 print_r($array1); 
 ?> 

Output

Original Array: 
 Array
 (
     [1] => red
     [2] => green
     [3] => blue
 )
 Sorted Array:  
 Array
 (
     [0] => blue
     [1] => green
     [2] => red
 ) 

Example 3

$b)? 1: 0;  
 } 
 // initializing the Input Array 1 
 $array1 = array(05=>"Reema", 10=>"raj", 30=>"Atul"); 
 echo("Original Array: \n");
 print_r($array1);
 // comparing the keys and values with additional index check 
 usort ($array1,"my_function");
 echo("\nSorted Array: \n");
 print_r($array1);
 ?> 

Output

Original Array: 
 Array
 (
     [5] => Reema
     [10] => raj
     [30] => Atul
 )
 Sorted Array: 
 Array 
 (
     [0] => Atul
     [1] => Reema
     [2] => raj
 )