replace every second comma of string using php

Question

I have a string of that displays like this:

1235, 3, 1343, 5, 1234, 1

I need to replace every second comma with a semicolon

i.e.

Answer 1

Try this :

$str     = '1235, 3, 1343, 5, 1234, 1';
$res_str = array_chunk(explode(",",$str),2);
foreach( $res_str as &$val){
   $val  = implode(",",$val);
}
echo implode(";",$res_str);