Partitions an array. Similar to array_chunk but goes through the array linearly

array_partition.php

<?php
/**
 * Partitions the array in a linear fashion.
 *
 * This is similar to array_chunk
 *
 * @param  array $ary        The array to partition
 * @param  int   $partitions How many partitions should the array be split into.
 *                           Default is to calculate off of the input array length
 * @return array
 */
function array_partition(array $ary, $partitions = null) {
	$ret    = array();
	$keys   = array_keys($ary);
	$length = count($keys);

	if ($partitions === null) {
		$partitions = round($length / 2);
	}
	
	for ($i = 0; $i < $length; ++$i){ 
	   	$ret[$i % $partitions][] = $ary[$keys[$i]];
	}

	return $ret;
}

// [ [1,4], [2,5], [3,6] ]
array_partition([1,2,3,4,5,6], 3);
array_partition([1,2,3,4,5,6]);    

// [ [1,3,5], [2,4,6] ]
array_partition([1,2,3,4,5,6], 2);