How do I pass JavaScript variables to PHP

Question

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    lt script type  text javascript  gt         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         lt  script gt    lt form name  myform  action   lt  php echo   SERVER   PHP SELF      gt   method  POST  gt       lt input type  hidden  name  hidden1  id  hidden1    gt   lt  form gt    lt  php     salarieid     POST  hidden1        query    select   from salarie where salarieid      salarieid     echo  query      result   mysql query  query     gt    lt table gt     Code for displaying the query result   lt  table gt

User · Accepted Answer

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 · Answer

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    lt  php if  isset   POST  hidden1          echo  You submitted    POST  hidden1         die     echo  lt  lt  lt HTML     lt form name  myform  action     SERVER  PHP SELF     method  post  id  myform  gt         lt input type  submit  name  submit  value  Test this mess     gt         lt input type  hidden  name  hidden1  id  hidden1    gt      lt  form gt       lt script type  text javascript  gt        document getElementById  hidden1   value    This is an example       lt  script gt  HTML    gt

User · Answer

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 -    lt  php      if isset   COOKIE  fbdata                echo  welcome     COOKIE  fbdata            gt

User · Answer

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    lt  PHP      COOKIE  height      gt    It s not a pretty solution  but it works

User · Answer

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

User · Answer

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 · Answer

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    lt  php if isset   POST       print r   POST       gt   lt form action   lt  php echo   SERVER  PHP SELF      gt   method  post  gt     lt input type  text  name  data  value  1    gt     lt input type  submit  value  Submit    gt   lt  form gt    Clicking submit will submit the page  and print out the submitted data

User · Answer

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      lt script gt  var username     lt  php echo  myname   gt    alert username    lt  script gt    the above code is correct and it will work  but the code below is totally wrong and it will never work    lt script gt      var username    syed ali       var  lt  php  myname   gt    username      alert myname        lt  script gt     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   lt input type  hidden  id  mydata  gt    then via jQuery or javaScript pass the value to the hidden field  like   lt script gt  var myvalue   55      mydata   val myvalue    lt  script gt    Now when you submit the form you can get the value in PHP

User · Answer

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 · Answer

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  amp  Cheers

User · Answer

There are several ways of passing variables from JavaScript to PHP  not the current page  of course    You could    Send the information in a form as stated here  will result in a page refresh  Pass it in Ajax  several posts are on here about that   without a page refresh  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

User · Answer

Here s how I did it  I needed to insert a local timezone into PHP    lt  php     ob start      gt    lt script type  text javascript  gt       var d   new Date        document write d getTimezoneOffset      lt  script gt    lt  php      offset   ob get clean        print r  offset

User · Answer

You can use JQuery Ajax and POST method  var obj                      document  ready function                   quot  button1 quot   click function                    var username    quot  username quot   val                    var password    quot  password quot   val        ajax       url   quot addperson php quot       type   quot POST quot        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   lt  php       username1   isset   POST  quot username quot        POST  quot username quot                    password1   isset   POST  quot password quot        POST  quot password quot           servername    quot xxxxx quot    username    quot xxxxx quot    password    quot xxxxx quot    dbname    quot xxxxx quot       Create connection  conn   new mysqli  servername   username   password   dbname      Check connection if   conn- gt connect error      die  quot Connection failed   quot     conn- gt connect error       sql    quot INSERT INTO user  username  password  VALUES    username1     password1    quot                           if   conn- gt query  sql      TRUE            echo json encode array  success    gt  1      else              echo json encode array  success    gt  0            conn- gt close      gt

User · Answer

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    lt img src  pic php  gt    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

User · Answer

Here is the Working example  Get javascript variable value on the same page in php    lt script gt  var p1    success    lt  script gt    lt  php echo   lt script gt document writeln p1   lt  script gt      gt

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