Why my mysql transaction is not working properly?

Question

I've been reading and gathering information for 2 days already and I give up. I have no clue why my piece of simple code is not succeeding.

I want to insert data from one form into two tables and YES I know there are exactly same problems described here and there, but as I said I'm familiar with them and also need to ask more questions.

The problem is in my query somewhere, at least this is what I believe it is.

Here it goes:

    unset($err);
//Variables
    $host = 'my.server.com';
    $user = '123';
    $pass = 'password';
    $dbname = '123';
    $err = array();
    $error_form = false;
    $img = "sth/sth.jpg";
//Connecting to the database using mysqli application programming interface
    $con = mysqli_connect($host, $user, $pass, $dbname);
if (!validate()) {
    if (!$con) {
        echo "Connection failed : <br />" . $new_con->connect_errno . "<br />" . $new_con->connect_error;
        exit;
    } else {
        echo "Connected! <br />";
    }
    var_dump($name);
    echo "<br />";
    var_dump($email);
    echo "<br />";
    var_dump($img);
    echo "<br />";
    $query= "START TRANSACTION;
            INSERT INTO `123`.`table1` (`name1`,`name2`) 
            VALUES ('". $name . "','". $email ."');
            INSERT INTO `123`.`table2` (`table1_id`,`name3`,`name4`) 
            VALUES (LAST_INSERT_ID(),'". $story . "','". $img ."');
            COMMIT;";
    var_dump(mysqli_query($con,$query));
    echo "<br />";
    $_POST["name"] = "";
    $_POST["email"] = "";
    $_POST["story"] = "";
}
//Form validation
function validate() {
    global $name, $email, $story, $err, $error_form;
    if($_SERVER['REQUEST_METHOD']=="POST") {
        if(isset($_POST["name"]) && !empty($_POST["name"])) {
            $name = htmlspecialchars($_POST["name"]);
        } else {
            $err[0] = "Name is missing.";
            $error_form = true;
        }
        if(isset($_POST["email"]) && !empty($_POST["email"])) {
            if (filter_var($_POST["email"], FILTER_VALIDATE_EMAIL)) {
                $email = htmlspecialchars($_POST["email"]);
            } else {
                $err[1] = "Email was verified as incorrect.";
                $error_form = true;
            }
        } else {
            $err[1] = "Email is missing.";
            $error_form = true;
        }
        if(isset($_POST["story"]) && !empty($_POST["story"])) {
            $story = htmlspecialchars($_POST["story"]);
        } else {
            $err[2] = "Your story does not contain any characters, it can't be submited.";
            $error_form = true;
        }
    }
    return $error_form;
}

Everything what confuses me happens here:

$query= "START TRANSACTION;
            INSERT INTO `123`.`table1` (`name1`,`name2`) 
            VALUES ('". $name . "','". $email ."');
            INSERT INTO `123`.`table2` (`table1_id`,`name3`,`name4`) 
            VALUES (LAST_INSERT_ID(),'". $story . "','". $img ."');
            COMMIT;";
    var_dump(mysqli_query($con,$query));

I've tried to SELECT the id FROM the table1 table and SET it as a @value instead of LAST_INSERT_ID(). I've tried to run two queries...many different solutions.

I found out when I dump mysqli_query($con,$query) it gives false every time unless I don't use transaction, so just simple queries, but I need them.

Last thing is should I use PDO instead of mysqli? Why?

and

Why to use mysqli object oriented style instead of procedural one?

Every help is appreciated. I would like more to understand than just to achieve the effect here.

Be aware this is my first post here, but not the first visit.

Answer 1

You can only do one query at a time with mysqli_query Look at mysqli_multi_query()

http://www.w3schools.com/php/func_mysqli_multi_query.asp

$query= "START TRANSACTION;
            INSERT INTO `123`.`table1` (`name1`,`name2`) 
            VALUES ('". $name . "','". $email ."');
            INSERT INTO `123`.`table2` (`table1_id`,`name3`,`name4`) 
            VALUES (LAST_INSERT_ID(),'". $story . "','". $img ."');
            COMMIT;";
    var_dump(mysqli_multi_query($con,$query));