javascript variable to php file and back using ajax

Question

i'm making an online barcode scanner application and having some issues with sending a javascript variable to php for my query , and getting it back in my html file with the data.

User scans barcode (studentNr) studentnr --> variable is going to be posted to the php file. in php file : query to compare with variable result of query --> back to the parameter of function(data) print result. Sounds easy, but how do I do this correctly?

Index.html :

 <head>

  <meta charset="utf-8" />
  <!-- Set the viewport width to device width for mobile -->
  <meta name="viewport" content="width=device-width" />
<script src="javascripts/jquery.js"></script>
</head>

<body>
 <div>

<input type="text" name="barcode" id="barcode"> // BARCODE SCAN
<input type="text" id="student" placeholder="studentenNaam" size="30"> //NAME FROM DB
               <!--  <input type="text" id="barcode" placeholder="Waiting for barcode scan..." size="40">
               <input type="text" id="student" placeholder="studentenNaam" size="30">-->

         </div>
// just the script for scanning the barcode :

    <script>
     var barcodeParsed = null;
     var studentenNr = null;
$(document).ready(function() {
    var pressed = false; 
    var chars = []; 
    $(window).keypress(function(e) {
        if (e.which >= 48 && e.which <= 57) {
            chars.push(String.fromCharCode(e.which));
        }
        console.log(e.which + ":" + chars.join("|"));
        if (pressed == false) {
            setTimeout(function(){
                if (chars.length >= 10) {
                    var barcode = chars.join("");
                    console.log("Barcode Scanned: " + barcode);
                    barcodeParsed = barcode;
                    var barcodeParsing = barcodeParsed.substring(5,11);
                    $("#barcode").val("s" + barcodeParsing);
                    studentenNr = "s" + barcodeParsing;

                }
                chars = [];
                pressed = false;
            },500);
        }
        pressed = true;
    });
});

$("#barcode").keypress(function(e){
    if ( e.which === 13 ) {
        console.log("Prevent form submit.");

        $.post('testdb.php', {'studnr' :studentenNr}, function(data){ //POST JS VAR TO PHP FILE
           $('#student').html(data); //RECEIVE DATA FROM DB INTO ID ELEMENT
        });
        e.preventDefault();
    }
});


     </script>

</body>

And in my testdb.php file it looks like this :

<?PHP

$studnr = htmlspecialchars($_POST['studnr']);
if(isset($studnr)){

    $user_name = "root";
$password = "";
$database = "Student";
$hostname = "127.0.0.1";

$db_handle = mysql_connect($hostname, $user_name, $password);
$db_found = mysql_select_db($database, $db_handle);

if ($db_found) {

$SQL = "SELECT * FROM student where studentenNr= '$studnr'"; 
$result = mysql_query($SQL);

while ( $db_field = mysql_fetch_assoc($result) ) {
/* Here needs the data to fetch*/
print $db_field['naam'] . "<BR>";
print $db_field['studentenNr'] . "<BR>";
print $db_field['voornaam'] . "<BR>";
}






mysql_close($db_handle);

}
else {

print "Database NOT Found ";
mysql_close($db_handle);

}

}

The problem is i can't receive any data from my html file in to my php file, plus i don't know how i can put the received data back in to my html file. in the php-file..How do I write it back to the html ? Do I need to use Ajax,Jquery,.. Any other solutions ?

Thank you for helping me out !

UPDATE

when adding this between the if(db_found) brackets I get an Internal Server Error 500.

 $sql = $db->prepare("select*from student where studentenNr= '$studnr' ");
$sql->execute($arraytest = array(':studnr' => studentenNr,naam );)


    $sql->execute(array(":studentenNr" => $studnr));

    $data = $sql->fetchAll();

    foreach($item as $data){
        print($item["naam"]);
        log($item["naam"]);

I don't see why your code does not work. You are sending an AJAX POST call to the php file and using the result (html) in your first page. Are you getting errors? (optionally) To make your app more robust I would recommend formatting your PHP output in JSON and doing some processing in the HTML side. — fbas
– fbas, Commented May 24, 2015 at 14:21

Alon Eitan · Accepted Answer · 2015-05-25 23:38:05Z

1

On your javascript you're sending studnr parameter:

$.post('testdb.php', {'studnr' :studentenNr}, function(data){

In your php script you trying to get the value from studentenNr parameter:

$studnr = htmlspecialchars($_POST['studentenNr']);

You need to cahnge your script to

$studnr = htmlspecialchars($_POST['studnr']);

Edit:

You're getting internal error because of this line:

$sql = $db->prepare("select*from student where studentenNr= '$studnr' ");

You need to prepare the SQL statement with the parameters and then bind them, so the line should be (something like):

$sql = $db->prepare("select * from student where studentenNr= :studnr");
$sql->execute(array(':studnr' => $studnr ));

edited May 25, 2015 at 23:38

answered May 24, 2015 at 14:25

Alon Eitan

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