How do I pass JavaScript variables to PHP?

user_198728 0
Viewed 744916

I want to pass JavaScript variables to PHP using a hidden input in a form.

But I can't get the value of $_POST['hidden1'] into $salarieid. Is there something wrong?

Here is the code:

<script type="text/javascript">
    // View what the user has chosen
    function func_load3(name) {
        var oForm = document.forms["myform"];
        var oSelectBox = oForm.select3;
        var iChoice = oSelectBox.selectedIndex;
        //alert("You have chosen: " + oSelectBox.options[iChoice].text);
        //document.write(oSelectBox.options[iChoice].text);
        var sa = oSelectBox.options[iChoice].text;
        document.getElementById("hidden1").value = sa;
    }
</script>

<form name="myform" action="<?php echo $_SERVER['$PHP_SELF']; ?>" method="POST">
    <input type="hidden" name="hidden1" id="hidden1" />
</form>

<?php
   $salarieid = $_POST['hidden1'];
   $query = "select * from salarie where salarieid = ".$salarieid;
   echo $query;
   $result = mysql_query($query);
?>

<table>
   Code for displaying the query result.
</table>
variables php javascript
16 Answers

You cannot pass variable values from the current page JavaScript code to the current page PHP code... PHP code runs at the server side, and it doesn't know anything about what is going on on the client side.

You need to pass variables to PHP code from the HTML form using another mechanism, such as submitting the form using the GET or POST methods.

<DOCTYPE html>
<html>
  <head>
    <title>My Test Form</title>
  </head>

  <body>
    <form method="POST">
      <p>Please, choose the salary id to proceed result:</p>
      <p>
        <label for="salarieids">SalarieID:</label>
        <?php
          $query = "SELECT * FROM salarie";
          $result = mysql_query($query);
          if ($result) :
        ?>
        <select id="salarieids" name="salarieid">
          <?php
            while ($row = mysql_fetch_assoc($result)) {
              echo '<option value="', $row['salaried'], '">', $row['salaried'], '</option>'; //between <option></option> tags you can output something more human-friendly (like $row['name'], if table "salaried" have one)
            }
          ?>
        </select>
        <?php endif ?>
      </p>
      <p>
        <input type="submit" value="Sumbit my choice"/>
      </p>
    </form>

    <?php if isset($_POST['salaried']) : ?>
      <?php
        $query = "SELECT * FROM salarie WHERE salarieid = " . $_POST['salarieid'];
        $result = mysql_query($query);
        if ($result) :
      ?>
        <table>
          <?php
            while ($row = mysql_fetch_assoc($result)) {
              echo '<tr>';
              echo '<td>', $row['salaried'], '</td><td>', $row['bla-bla-bla'], '</td>' ...; // and others
              echo '</tr>';
            }
          ?>
        </table>
      <?php endif?>
    <?php endif ?>
  </body>
</html>
user_1024470

when your page first loads the PHP code first run and set the complete layout of your webpage. after the page layout, it set the JavaScript load up. now JavaScript directly interacts with DOM and can manipulate the layout but PHP can't it needs to refresh the page. There is only way is to refresh your page to and pass the parameters in the page URL so that you can get the data via PHP. So we use AJAX to interact Javascript with PHP without page reload. AJAX can also be used as an API. one more thing if you have already declared the variable in PHP. before the page load then you can use it with your Javascript example.

<script>
var username = "<?php echo $myname;?>";
alert(username);
</script>

the above code is correct and it will work. but the code below is totally wrong and it will never work.

<script>
    var username = "syed ali";
    var <?php $myname;?> = username;
    alert(myname);
    </script>

  • Pass value from JavaScript to PHP via AJAX

    it is the most secure way to do it. because HTML content can be edited via developer tools and the user can manipulate the data. so it is better to use AJAX if you want security over that variable.if you are a newbie to AJAX please learn AJAX it is very simple.

The best and most secure way to pass JavaScript variable into PHP is via AJAX

simple AJAX example 

var mydata = 55;
var myname = "syed ali";
var userdata = {'id':mydata,'name':myname};
    $.ajax({
            type: "POST",
            url: "YOUR PHP URL HERE",
            data:userdata, 
            success: function(data){
                console.log(data);
            }
            });
  • PASS value from javascript to php via hidden fields.

otherwise, you can create hidden HTML input inside your form. like

<input type="hidden" id="mydata">

then via jQuery or javaScript pass the value to the hidden field. like

<script>
var myvalue = 55;
$("#mydata").val(myvalue);
</script>

Now when you submit the form you can get the value in PHP.

user_99785350

PHP runs on the server before the page is sent to the user, JavaScript is run on the user's computer once it is received, so the PHP script has already executed.

If you want to pass a JavaScript value to a PHP script, you'd have to do an XMLHttpRequest to send the data back to the server.

Here's a previous question that you can follow for more information: Ajax Tutorial

Now if you just need to pass a form value to the server, you can also just do a normal form post, that does the same thing, but the whole page has to be refreshed.

<?php
if(isset($_POST))
{
  print_r($_POST);
}
?>
<form action="<?php echo $_SERVER['PHP_SELF']; ?>" method="post">
  <input type="text" name="data" value="1" />
  <input type="submit" value="Submit" />
</form>

Clicking submit will submit the page, and print out the submitted data.

user_236660

You can use JQuery Ajax and POST method:

var obj;

                
$(document).ready(function(){
            $("#button1").click(function(){
                var username=$("#username").val();
                var password=$("#password").val();
  $.ajax({
    url: "addperson.php",
    type: "POST", 
    async: false,
    data: {
        username: username,
        password: password
    }
})
.done (function(data, textStatus, jqXHR) { 
    
   obj = JSON.parse(data);
   
})
.fail (function(jqXHR, textStatus, errorThrown) { 
    
})
.always (function(jqXHROrData, textStatus, jqXHROrErrorThrown) { 
    
});
  
 
            });
        });

To take a response back from the php script JSON parse the the respone in .done() method. Here is the php script you can modify to your needs:

<?php
     $username1 = isset($_POST["username"]) ? $_POST["username"] : '';
    
     $password1 = isset($_POST["password"]) ? $_POST["password"] : '';

$servername = "xxxxx";
$username = "xxxxx";
$password = "xxxxx";
$dbname = "xxxxx";

// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);
// Check connection
if ($conn->connect_error) {
  die("Connection failed: " . $conn->connect_error);
}

$sql = "INSERT INTO user (username, password)
VALUES ('$username1', '$password1' )";

    ;  
    
    
   

if ($conn->query($sql) === TRUE) {
    
   echo json_encode(array('success' => 1));
} else{
    
    
  echo json_encode(array('success' => 0));
}





$conn->close();
?>
user_62014540

Is your function, which sets the hidden form value, being called? It is not in this example. You should have no problem modifying a hidden value before posting the form back to the server.

user_2269170

This obviously solution was not mentioned earlier. You can also use cookies to pass data from the browser back to the server.

Just set a cookie with the data you want to pass to PHP using javascript in the browser.

Then, simply read this cookie on the PHP side.

user_29202100

We cannot pass JavaScript variable values to the PHP code directly... PHP code runs at the server side, and it doesn't know anything about what is going on on the client side.

So it's better to use the AJAX to parse the JavaScript value into the php Code.

Or alternatively we can make this done with the help of COOKIES in our code.

Thanks & Cheers.

user_85787310

Use the + sign to concatenate your javascript variable into your php function call.

 <script>
     var JSvar = "success";
     var JSnewVar = "<?=myphpFunction('" + JSvar + "');?>";
 </script>`

Notice the = sign is there twice.

user_19361190
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