gistfile1.php

<?php

$array = array("1","2","3","4","5","6","7","8","9","10","11","12","13","14","15");

echo "<pre>";


function AddElementToArrayAfter($array = "", $element = "", $after = "") {

 $count = 0;
 foreach ($array as $k => $v) 
        {   
                // insert new object
                if ($count)
                {   
                        if ($k % $after == 1) {
                        	$return[$k] = $element;
                        }
                }   
                // insert old object
                $return[$k] = $v; 
                $count++;
        }   


       return $return;
}


$a = AddElementToArrayAfter($array, 'BREAK', 4);


print_r($a);