php - How to ensure data inserted only once at a time? -

this how json like:

$return='{"sub":{"2":""},"postcode":"56000","slider1":"100","action":"test"}';   $data = json_decode($return, true); 

this how value,

$postcode=$data['postcode']; $budget = $data['slider1']; $subject =$data['sub'];  var_dump($key =array_keys($data['sub']));// prints 0=>2  foreach($key $key1=>$key2) {      $key1;//prints 0      $key2;//prints 2 }  $key2;//prints 2 

i'm inserting data this:

try {   //$pdo = new pdo('mysql:host=localhost;dbname=users', $username, $password);   //$pdo->setattribute(pdo::attr_errmode, pdo::errmode_exception);   include($_server['document_root'].'/config.php');   $stmt = $pdo->prepare('insert test (postcode,budget,subject) values(:postcode,:budget,:subject)');   $stmt->execute(array(     ':postcode' => $postcode,     ':budget'=> $budget,     ':subject'=> $key2   ));    # affected rows?   $stmt->rowcount(); // 1 } catch(pdoexception $e) {   'error: ' . $e->getmessage(); } 

the above query inserts data twice database. checked network tab in chrome dev tool, shows request file sent twice.

is there way insert data once @ time? mean there way place restriction on query?

edited

ajax

$("document").ready(function(){           $(".form").submit(function(){             var data = {               "action": "test"             };             data = $(this).serialize();             $.ajax({               type: "post",               datatype: "json",               url: "writedb.php", //relative or absolute path writedb.php file       data: data,                   success: function(data) {     //.....     }