How to refer to the second occurrence of a string in php?

I’ve been trying to replace my second occurrence for a certain character
For Example: Hey, I'm trying something With PHP, Is it Working?
I need to get the position of the second comma, I’ve tried to use strpos but in vain because it’s define that it finds the first occurrence of a string so I got Position: 3, any one knows a solution?

Answer

The strpos function accepts an optional third parameter which is an offset from which the search for the target string should begin. In this case, you may pass a call to strpos which finds the first index of comma, incremented by one, to find the second comma.

$input = "Hey, I'm trying something With PHP, Is it Working?";
echo strpos($input, ",", strpos($input, ",") + 1);  // prints 34

Just for completeness/fun, we could also use a regex substring based approach here, and match the substring up the second comma:

$input = "Hey, I'm trying something With PHP, Is it Working?";
preg_match("/^[^,]*,[^,]*,/", $input, $matches);
echo strlen($matches[0]) - 1;  // also prints 34