try {
    mysql_connect();
    $result = mysql_query($query);
    while($data = mysql_fetch_row($result)){
        $fileContent = file_get_contents($data['file']);
        if(strpos($fileContent,'asdfg') !== 0){
            throw new myException();
        }
        //...
    }
    $message = 'все нормально';
} catch (myException $e) {
    $message = 'ошибка';
} catch (ErrorException $e) {
    $message = 'ошибка';
}
echo $message;