PHP shuffle() Function

The shuffle() Function is a builtin function in PHP and is used to shuffle or randomize the order of the elements in an array. This function assigns new keys for the elements in the array. It will also remove any existing keys, rather than just reordering the keys and assigns numeric keys starting from zero.

Syntax:

boolean shuffle($array)

Parameter: This function accepts a single parameter $array. It specifies the array we want to shuffle.

Return Value: This function returns a boolean value i.e., either True or False. It returns TRUE on success and FALSE on failure.

Note: This function will work for PHP version 4+.

Examples:  

Input:- array("a"=>"Ram", 
              "b"=>"Shita", 
              "c"=>"Geeta", 
              "d"=>"geeksforgeeks" )
Output:- array( [0] => Geeta,
                [1] => Shita,
                [2] => Ram,
                [3] => geeksforgeeks )
Explanation: Here as we can see that input contain elements 
             in a order but in output order become shuffled.

Below programs illustrates the working of shuffle() in PHP:  

• When the input array is an associative array, then the shuffle() function will randomize the order of elements as well as assigns new keys to the elements starting from zero (0).

PHP

<?php

// input array contain some elements which
// need to be shuffled.
$a = array
     (
        "a"=>"Ram",
        "b"=>"Shita",
        "c"=>"Geeta",
        "d"=>"geeksforgeeks"
     );

shuffle($a);
print_r($a);

?>

Output: 

Array
(
    [0] => geeksforgeeks
    [1] => Shita
    [2] => Ram
    [3] => Geeta
)

• When the input array is not associative then the shuffle() function will randomize the order and convert the array to an associative array with keys starting from zero (0).

PHP

<?php

// input array contain some elements
// which need to be shuffled.
$a = array
     (
        "ram",
        "geeta",
        "blue",
        "red",
        "shyam"
     );

shuffle($a);
print_r($a);

?>

Output: 

Array
(
    [0] => red
    [1] => geeta
    [2] => ram
    [3] => shyam
    [4] => blue
)

Reference: 
http://php.net/manual/en/function.shuffle.php