How to extract a substring from a string in PHP until it reaches a certain character?

Question

I have part of a PHP application which assess a long string input by the user, and extracts a number which always begins 20 characters into the string the user supplies.

Answer 1

Going to just add on to Gumbo's answer in case you need help with the substring function:

$pos = strpos($str, '"', 20);
$substring = substr($str, 20, $pos);