Well you can use this :
function my_implode($separator,$array){
$temp = '';
foreach($array as $key=>$item){
$temp .= $item;
if($key != sizeof($array)-1){
$temp .= $separator ;
}
}//end of the foreach loop
return $temp;
}//end of the function
$array = array("One", "Two", "Three","Four");
$str = my_implode('-',$array);
echo $str;
Hope it helps you