使用php将数据从html表单插入数据库

i have build following form it works 100%. only one problem. when i open this page a blank data insert to database every time with out press any submit button.

I do not want to use php on seprate file like action="php/doctor.php" I do want to use php on same page of html form.

<?php
$servername = "localhost";
$username = "root";
$password = "";

?>
<?php
if (isset($_POST["dname"]))
{
    $dname = $_POST['dname'];
} else {
    $dname = null;
}


if (isset($_POST["mobile"]))
{
    $mobile = $_POST['mobile'];
} else {
    $mobile = null;
}


if (isset($_POST["dusername"]))
{
    $dusername = $_POST['dusername'];
} else {
    $dusername = null;
}

if (isset($_POST["dpassword"]))
{
    $dpassword = $_POST['dpassword'];
} else {
    $dpassword = null;
}

try {
    $conn = new PDO("mysql:host=$servername;dbname=team", $username, $password);
    // set the PDO error mode to exception

    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    $sql = "INSERT INTO doctor (dname, mobile, dusername, dpassword)
        VALUES ('$dname', '$mobile', '$dusername', '$dpassword')";
    // use exec() because no results are returned
    $conn->exec($sql);
    echo '<div class="alert alert-success alert-dismissible">
        <a href="#" class="close" data-dismiss="alert" aria-label="close">&times;</a>
        <strong>Success!</strong> Indicates a successful or positive action.
        </div>';

}
catch(PDOException $e)
{
    echo $sql . "<br>" . $e->getMessage();
}

$conn = null;
?>

<script src="bootstrap/js/bootstrap.min.js"></script>
<script src="bootstrap/jquery-1.12.3.min.js"></script>

<link rel="stylesheet" href="bootstrap/css/bootstrap.min.css">
<link rel="stylesheet" href="style/team.css">
<link rel="stylesheet" href="style/teams.css">
<script src="js/javas.js"></script>

</head>
<body >

<form class="form-horizontal" action="doctor.php" method="post"  role="form">
    <div class="form-group">
        <label class="control-label col-sm-2" >Doctor Name:</label>
        <div class="col-sm-8">
            <input type="text" class="form-control" name="dname" placeholder="Enter email">
        </div>
    </div>
    <div class="form-group">
        <label class="control-label col-sm-2" >Mobile:</label>
        <div class="col-sm-8">
            <input type="text" class="form-control" name="mobile" placeholder="Enter mobile">
        </div>
    </div>
    <div class="form-group">
        <label class="control-label col-sm-2">User name:</label>
        <div class="col-sm-8">
            <input type="text" class="form-control" name="dusername" placeholder="Enter username">
        </div>
    </div>
    <div class="form-group">
        <label class="control-label col-sm-2">Password:</label>
        <div class="col-sm-8"> 
            <input type="password" class="form-control" name="dpassword" placeholder="Enter password">
        </div>
    </div>
    <div class="form-group"> 
        <div class="col-sm-offset-2 col-sm-10">
            <button type="submit" class="btn btn-default">Submit</button>
        </div>
    </div>
</form>
</div>

You can use somethings like this

if(isset($_POST['submit'])) {
// Enter the Code you want to execute after the form has been submitted

} else {
// Display the Form and the Submit Button
}

Here's a complete example:

<?php    
    if(isset($_POST['SubmitButton'])) { //check if form was submitted
        $input = $_POST['inputText']; //get input text
        echo "Success! You entered: " . $input;
    }    
?>
<html>
    <body>    
        <form action="" method="post">
            <input type="text" name="inputText"/>
            <input type="submit" name="SubmitButton"/>
        </form>    
    </body>
</html>

The issue here is "logic".

Firstly, name your submit button, it will be needed.

<button name="submit" type="submit" class="btn btn-default">Submit</button>

Then apply the logic I stated in comments:

if button is set... if all POSTs are not empty/query.

Note comments in the code below, I want you to do this and you will "learn" from it which is the ultimate goal here.

Sidenote: You can substitute && (AND) for || (OR).
Consult http://php.net/manual/en/language.operators.logical.php on logic operators.

if (isset($_POST["submit"])){

    if (!empty($_POST["dname"]) && 

        !empty($_POST["mobile"]) &&

        !empty($_POST["dusername"]) && 

        !empty($_POST["dpassword"])

)

    {

    $dname = $_POST["dname"];
    // Do the same for the other POST arrays

    // Place your query in here
    }

}

You can also a ternary operator inside the if (isset($_POST["submit"])) conditional statement and assigning NULL as a default if left empty.

Reference:

http://php.net/manual/en/language.operators.comparison.php

Example pulled from it:

$action = (empty($_POST['action'])) ? 'default' : $_POST['action'];

and apply that logic to your code.

Also as stated in comments; use a prepared statement and hash your passwords.

References: