- var_dump: documentation ( source)
- preg_split: documentation ( source)
<?php
$str = 'temp1, temp2, temp3, temp4, temp5, temp6, temp7, temp8, temp9, temp10';
$times = 4;
[$string1, $string2] = preg_split("/(?:[^,]+,? ?){0,$times}\K/", $str, 2);
var_dump($string1, $string2);