<?php
$pattern = "/^(?=.*[A-Z])(?=.*[0-9])[A-Z0-9]{8}$/i";
echo preg_match($pattern, "A1234567") . "\n";
echo preg_match($pattern, "A123456A") . "\n";
echo preg_match($pattern, "12345678") . "\n";
echo preg_match($pattern, "AAAAAAAA") . "\n";
?>