PHP分离字符串--分离n个空格成数组

<?php
    $space = "                    ";//最大的空格数
	$length = strlen($space);
	for ($i=0; $i < $length; $i++) { 

		$str = str_replace($space,":", $str);
		$space = substr($space, 0, strlen($space)-1);
	}
	$str_explode = explode(":", $str);
?>