Access a JavaScript variable from PHP

Question

I need to access a JavaScript variable with PHP  Here s a stripped-down version of the code I m currently trying  which isn t working    lt script type  text javascript  charset  utf-8  gt      var test    tester    lt  script gt    lt  php     echo   GET  test      gt    I m a completely new to both JavaScript and PHP  so I would really appreciate any advice   UPDATE  OK  I guess I simplified that too much  What I m trying to do is create a form that will update a Twitter status when submitted  I ve got the form working OK  but I want to also add geolocation data  Since I m using Javascript  specifically  the Google Geolocation API  to get the location  how do I access that information with PHP when I m submitting the form

User · Answer

As JavaScript is a client-side language and PHP is a server-side language you would need to physically push the variable to the PHP script, by either including the variable on the page load of the PHP script (script.php?var=test), which really has nothing to do with JavaScript, or by passing the variable to the PHP via an AJAX/AHAH call each time the variable is changed.

If you did want to go down the second path, you'd be looking at XMLHttpRequest, or my preference, jQuerys Ajax calls: http://docs.jquery.com/Ajax

User · Answer

Well the problem with the GET is that the user is able to change the value by himself if he has some knowledges  I wrote this so that PHP is able to retrive the timezone from Javascript       -- index php   lt  php   if   isset   COOKIE  timezone         gt   lt html gt   lt script language  javascript  gt      var d   new Date       var timezoneOffset   d getTimezoneOffset     60       the cookie expired in 3 hours   d setTime d getTime    3 60 60 1000      var expires      expires   d toGMTString      document cookie    timezone      timezoneOffset   expires      path       document location href  index php   lt  script gt   lt  html gt   lt  php   else       gt      lt html gt     lt head gt     lt body gt      lt  php    if isset   COOKIE  timezone           dump var   COOKIE  timezone               gt

User · Answer

The short answer is you can t   I don t know any PHP syntax  but what I can tell you is that PHP is executed on the server and JavaScript is executed on the client  on the browser    You re doing a   GET  which is used to retrieve form values      The built-in   GET function is used to collect values in a form with method  get     In other words  if on your page you had    lt form method  get  action  blah php  gt       lt input name  test  gt  lt  input gt   lt  form gt    Your   GET call would retrieve the value in that input field   So how to retrieve a value from JavaScript   Well  you could stick the javascript value in a hidden form field      lt script type  text javascript  charset  utf-8  gt      var test    tester          find the  test  input element and set its value to the above variable     document getElementByID  test   value   test   lt  script gt       elsewhere on your page       lt form method  get  action  blah php  gt       lt input id  test  name  test  visibility  hidden  gt  lt  input gt       lt input type  submit  value  Click me   gt  lt  input gt   lt  form gt    Then  when the user clicks your submit button  he she will be issuing a  GET  request to blah php  sending along the value in  test

User · Answer

JS ist browser-based  PHP is server-based  You have to generate some browser-based request signal to get the data from the JS into the PHP  Take a look into Ajax

User · Answer

GET accesses query string variables  test is not a querystring variable  PHP does not process the JS in any way    You need to rethink   You could make a php variable  test  and do something like    lt  php  test    tester     gt   lt script type  text javascript  charset  utf-8  gt      var test     lt  php echo  test  gt     lt  script gt    lt  php     echo  test    gt    Of course  I don t know why you want this  so I m not sure the best solution   EDIT  As others have noted  if the JavaScript variable is really generated on the client  you will need AJAX or a form to send it to the server

User · Answer

If showing data to the user  do a redirect    lt script language  JavaScript  gt      var tester    foobar       document location  http   www host org myphp php test     tester   lt  script gt    or an iframe    lt script language  JavaScript  gt      var tester    foobar       document write   lt iframe src   http   www host org myphp php test     tester       gt  lt  iframe gt      lt  script gt    If you don t need user output  create an iframe with width 0 and height 0

User · Answer

I m looking at this and thinking  if you can only get variables into php in a form  why not just make a form and put a hidden input in the thing so it doesn t show on screen  and then put the value from your javascript into the hidden input and POST that into the php  It would sure be a lot less hassle than some of this other stuff right

User · Answer

try adding this to your js function           var outputvar   document getElementById  your div id inside html form        outputvar innerHTML   lt input id id to send to php value   your js var   gt      Later in html        lt div id  id you choosed for outputvar  gt  lt  div gt    this div will contain the js var to be passed through a form to another js function or to php  remember to place it inside your html form   This solution is working fine for me   In your specific geolocation case you can try adding the following to function showPosition position        var outputlon   document getElementById  lon1        outputlon innerHTML     lt input id lon value   lon   gt        var outputlat   document getElementById  lat1        outputlat innerHTML     lt input id lat value   lat   gt        later add these div to your html form    lt div id lat1 gt  lt  div gt   lt div id lon1 gt  lt  div gt    In these div you ll get latitude and longitude as input values for your php form  you would better hide them using css  show only the marker on a map if used  in order to avoid users to change them before to submit  and set your database to accept float values with lenght 10 7   Hope this will help

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