How do I pass JavaScript variables to PHP?

157
votes

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>
15
phpjavascriptvariables
You can store the js variable value in a cookie and later access that variable in php cookie. – shasi kanth
@shasikanth - you can do that, but the cookie won't be set until the second time the page is viewed. And at that time, it will be the value from the first page view - it is always one behind. A cookie is not a mechanism to dynamically pass info back to server; you have to do something else to refresh the page, e.g. POST a form, or make an Ajax call. And if you are doing one of those, there is no reason to use a cookie - just pass the info in the mechanism you are using. Also, a cookie will persist after the page is gone - not what is intended in this question. – ToolmakerSteve

15 Answers

103
votes

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>
30
votes

Just save it in a cookie:

$(document).ready(function () {
  createCookie("height", $(window).height(), "10");
});

function createCookie(name, value, days) {
  var expires;
  if (days) {
    var date = new Date();
    date.setTime(date.getTime() + (days * 24 * 60 * 60 * 1000));
    expires = "; expires=" + date.toGMTString();
  }
  else {
    expires = "";
  }
  document.cookie = escape(name) + "=" + escape(value) + expires + "; path=/";
}

And then read it with PHP:

<?PHP
   $_COOKIE["height"];
?>

It's not a pretty solution, but it works.

20
votes

There are several ways of passing variables from JavaScript to PHP (not the current page, of course).

You could:

  1. Send the information in a form as stated here (will result in a page refresh)
  2. Pass it in Ajax (several posts are on here about that) (without a page refresh)
  3. Make an HTTP request via an XMLHttpRequest request (without a page refresh) like this:
 if (window.XMLHttpRequest){
     xmlhttp = new XMLHttpRequest();
 }

else{
     xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
 }

 var PageToSendTo = "nowitworks.php?";
 var MyVariable = "variableData";
 var VariablePlaceholder = "variableName=";
 var UrlToSend = PageToSendTo + VariablePlaceholder + MyVariable;

 xmlhttp.open("GET", UrlToSend, false);
 xmlhttp.send();

I'm sure this could be made to look fancier and loop through all the variables and whatnot - but I've kept it basic as to make it easier to understand for the novices.

14
votes

Here is the Working example: Get javascript variable value on the same page in php.

<script>
var p1 = "success";
</script>

<?php
echo "<script>document.writeln(p1);</script>";
?>
8
votes

Here's how I did it (I needed to insert a local timezone into PHP:

<?php
    ob_start();
?>

<script type="text/javascript">

    var d = new Date();
    document.write(d.getTimezoneOffset());
</script>

<?php
    $offset = ob_get_clean();
    print_r($offset);
7
votes

I was trying to figure this out myself and then realized that the problem is that this is kind of a backwards way of looking at the situation. Rather than trying to pass things from JavaScript to php, maybe it's best to go the other way around, in most cases. PHP code executes on the server and creates the html code (and possibly java script as well). Then the browser loads the page and executes the html and java script.

It seems like the sensible way to approach situations like this is to use the PHP to create the JavaScript and the html you want and then to use the JavaScript in the page to do whatever PHP can't do. It seems like this would give you the benefits of both PHP and JavaScript in a fairly simple and straight forward way.

One thing I've done that gives the appearance of passing things to PHP from your page on the fly is using the html image tag to call on PHP code. Something like this:

<img src="pic.php">

The PHP code in pic.php would actually create html code before your web page was even loaded, but that html code is basically called upon on the fly. The php code here can be used to create a picture on your page, but it can have any commands you like besides that in it. Maybe it changes the contents of some files on your server, etc. The upside of this is that the php code can be executed from html and I assume JavaScript, but the down side is that the only output it can put on your page is an image. You also have the option of passing variables to the php code through parameters in the url. Page counters will use this technique in many cases.

7
votes

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.

6
votes

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.

5
votes

We can easily pass values even on same/ different pages using the cookies shown in the code as follows (In my case, I'm using it with facebook integration) -

function statusChangeCallback(response) {
    console.log('statusChangeCallback');
    if (response.status === 'connected') {
        // Logged into your app and Facebook.
        FB.api('/me?fields=id,first_name,last_name,email', function (result) {
            document.cookie = "fbdata = " + result.id + "," + result.first_name + "," + result.last_name + "," + result.email;
            console.log(document.cookie);
        });
    }
}

And I've accessed it (in any file) using - 

<?php 
    if(isset($_COOKIE['fbdata'])) { 
        echo "welcome ".$_COOKIE['fbdata'];
    }
?>
3
votes

Your code has a few things wrong with it.

  • You define a JavaScript function, func_load3(), but do not call it.
  • Your function is defined in the wrong place. When it is defined in your page, the HTML objects it refers to have not yet been loaded. Most JavaScript code checks whether the document is fully loaded before executing, or you can just move your code past the elements it refers to in the page.
  • Your form has no means to submit it. It needs a submit button.
  • You do not check whether your form has been submitted.

It is possible to set a JavaScript variable in a hidden variable in a form, then submit it, and read the value back in PHP. Here is a simple example that shows this:

<?php
if (isset($_POST['hidden1'])) {
   echo "You submitted {$_POST['hidden1']}";
   die;
}

echo <<<HTML
   <form name="myform" action="{$_SERVER['PHP_SELF']}" method="post" id="myform">
      <input type="submit" name="submit" value="Test this mess!" />
      <input type="hidden" name="hidden1" id="hidden1" />
   </form>

   <script type="text/javascript">
      document.getElementById("hidden1").value = "This is an example";
   </script>
HTML;
?>
2
votes

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.

1
votes

May be you could use jquery serialize() method so that everything will be at one go.

var data=$('#myForm').serialize();

//this way you could get the hidden value as well in the server side.

1
votes

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();
?>
0
votes

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.

0
votes

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.