preg_match不区分大小写，无法注册

Question

尝试验证注册页面，不区分大小写。

if(preg_match('[^a-z]', substr($username, 0, 1)))
        $errors['username']['start_type'] = ' Username must begin with a letter. Please try again.'; 

if(preg_match('[^a-z]', substr($username, 0, 1)))
        $errors['username']['start_type'] = ' Username must begin with a letter. Please try again.';