If you want to have a string BETWEEN two strings, just use this function:
<?php
function get_between($input, $start, $end)
{
$substr = substr($input, strlen($start)+strpos($input, $start), (strlen($input) - strpos($input, $end))*(-1));
return $substr;
}
//Example:
$string = "123456789";
$a = "12";
$b = "9";
echo get_between($string, $a, $b);
//Output:
//345678
?>