html form, PHP insert data into database not working?

Question

I have HTML registration form when I submit the form the PHP code appears and data not insert to database i made my database using phpMyAdmin, what should I do?

Here my PHP code:

     <?php
        $con=mysqli_connect('localhost','root','');
        $db=mysqli_select_db($con,'research_sys');
    if ($con) {
        echo "good";
        }else {
        die('error');
        }
        if(isset($_POST['submit'])){
$Fname = mysqli_real_escape_string($con,$_POST["Fname"]);
$Lname = mysqli_real_escape_string($con,$_POST["Lname"]);
$email = mysqli_real_escape_string($con,$_POST['email']);
$password = mysqli_real_escape_string($con,$_POST['password']);
    $sql =  mysqli_query($con,"INSERT INTO `research_sys`.`researcher` (Re_fname,Re_lname,Re_mobile,Re_password) values ('$Fname','$Lname','$email','$password ')");

            if (mysqli_query($sql)){
            echo "insert";
            } else {
                echo "error" .$sql ."<br>". mysqli_error($con);
                }           
}
?>

here my registration HTML code

            <form method="post" action="connect.php">
                <legend class="center">Register </legend>
                <br>
                <div>

                    <input type="text" name="Fname" placeholder="First Name"/>
                </div>
                <div>

                    <input type="text" name="Lname" placeholder="Last Name"/>
                </div>

                <div>
                    <input type="text" name="email" placeholder="Email"/>
                </div>

                <div>
                    <input type="password" name="password" placeholder="Password"/>
                </div>

                <div>
                    <input type="password" name="con_password" placeholder="Password confirm"/>
                </div>
                <input type="submit" name="submit" value="submit"/>
            </form>

Answer 1

Look at the following:

$sql =  mysqli_query($con,"INSERT INTO `research_sys`.`researcher` 
        ^^^^^^^^^^^^ function

        (Re_fname,Re_lname,Re_mobile,Re_password) 
        values ('$Fname','$Lname','$email','$password ')");
                                                     ^ space

    if (mysqli_query($sql)){
        ^^^^^^^^^^^^ function

You're using that mysqli_query() function twice, remove one and just do:

if ($sql){...}

and mysqli_error($con) should have thrown you an error about it.

If it didn't throw an error, then that may suggest you're using this as file:/// as opposed to http://localhost.

Edit:

"i have html registration form whin i submit the form the php code apears"

That's because of what I wrote above before quoting you. You need to run this off a webserver with php/mysql installed and running properly and as http://localhost.

Also, remove the space in this '$password '. That space counts as a character.

• Double-check your column names also. There seems to be something that doesn't match (Re_fname,Re_lname,Re_mobile,Re_password) the Re_mobile and you're referencing an email '$email' in VALUES.

You also seem to store plain text passwords; don't, it's not safe if you intend on going live with this. Use password_hash() and a prepared statement.

---

Footnotes:

    $con=mysqli_connect('localhost','root','');
    $db=mysqli_select_db($con,'research_sys');

You can shorten that to using all 4 arguments in mysqli_connect():

    $con=mysqli_connect('localhost','root', '', 'research_sys');