Reorder a PHP array, moving items up or down

gistfile1.php

<?php
/*
 A quick set of functions to move items in a non-associative array
 up or down by one, shifting the items around it appropriately.
 
 Original usage was to for a set of UP and DOWN buttons to 
 manipulate the order of an array of items stored in Wordpress option.
*/

$a = array('a','b','c','d','e');

function down($a,$x) {
	if( count($a)-1 > $x ) {
		$b = array_slice($a,0,$x,true);
		$b[] = $a[$x+1];
		$b[] = $a[$x];
		$b += array_slice($a,$x+2,count($a),true);
		return($b);
	} else { return $a; }
}

function up($a,$x) {
	if( $x > 0 and $x < count($a) ) {
		$b = array_slice($a,0,($x-1),true);
		$b[] = $a[$x];
		$b[] = $a[$x-1];
		$b += array_slice($a,($x+1),count($a),true);
		return($b);
	} else { return $a; }
}

// Start
print_r($a);
/* Output
Array
(
    [0] => a
    [1] => b
    [2] => c
    [3] => d
    [4] => e
)
*/

// Move item 4 up
print_r(up($a,4));
/* Output
Array
(
    [0] => a
    [1] => b
    [2] => c
    [3] => e
    [4] => d
)
*/

// Move item 0 down
print_r(down($a,0));
/* Output
Array
(
    [0] => b
    [1] => a
    [2] => c
    [3] => d
    [4] => e
)
*/

// Test, move the bottom item down (ie. do nothing)
print_r(down($a,4));
/* Output
Array
(
    [0] => a
    [1] => b
    [2] => c
    [3] => d
    [4] => e
)
*/

// Test, move the top item up (ie. do nothing)
print_r(up($a,0));
/* Output
Array
(
    [0] => a
    [1] => b
    [2] => c
    [3] => d
    [4] => e
)
*/

Good implementation √

Have a look to my gist, which gives you ability to add new item to the array or change position of existing item, after shifting items up or down depending on available positions.
https://gist.github.com/wajdijurry/a00752123134342ccc9d13a480c9f013