How to get JavaScript variable value in PHP

Question

I want the value of JavaScript variable which i could access using PHP   I am using the code below but it doesn t return value of that variable in PHP      set global variable in javascript     profile viewer uid   1         php code   profile viewer uid   POST  profile viewer uid       this gives me the following error  -  A PHP Error was encountered Severity  Notice Message  Undefined index  profile viewer uid   Another php code i used which give empty value   profile viewer uid     lt script language javascript gt document write profile viewer uid   lt  script gt    When I echo it shows nothing

User · Answer

You need to add this value to the form data that is submitted to the server  You can use   lt input type  hidden  value  1  name  profile viewer uid  id  profile viewer uid  gt    inside your form tag

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These are two different languages  that run at different time - you cannot interact with them like that   PHP is executed on the server while the page loads  Once loaded  the JavaScript will execute on the clients machine in the browser

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Here is the Working example  Get javascript variable value on the same page    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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PHP runs on the server  It outputs some text  Then it stops running    The text is sent to the client  a browser   The browser then interprets the text as HTML and JavaScript   If you want to get data from JavaScript to PHP then you need to make a new HTTP request and run a new  or the same  PHP script   You can make an HTTP request from JavaScript by using a form or Ajax

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You might want to start by learning what Javascript and php are  Javascript is a client side script language running in the browser of the machine of the client connected to the webserver on which php runs  These languages can not communicate directly   Depending on your goal you ll need to issue an AJAX get or post request to the server and return a json xml html whatever response you need and inject the result back in the DOM structure of the site  I suggest Jquery  BackboneJS or any other JS framework for this  See the Jquery documentation for examples   If you have to pass php data to JS on the same site you can echo the data as JS and turn your php data using json encode   into JS    lt script type  text javascript gt      var foo    lt  php echo json encode  somePhpVar     gt   lt  script gt

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This could be a little tricky thing but the secure way is to set a javascript cookie  then picking it up by php cookie variable Then Assign this php variable to an php session that will hold the data  more securely than cookie Then delete the cookie using javascript and redirect the page to itself  Given that you have added an php command to catch the variable  you will get it

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Add a cookie with the javascript variable you want to access   document cookie  profile viewer uid 1     Then acces it in php via   profile viewer uid     COOKIE  profile viewer uid

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If you want to use a js variable in a php script you MUST pass it within a HTTP request   There are basically two ways    Submitting or reloading the page  as per Chris answer   Using AJAX  which is made exactly for communicating between a web page  js  and the server php  without reloading changing the page    A basic example can be   var profile viewer uid   1    ajax     url   serverScript php     method   POST     data     profile viewer uid   profile viewer uid        And in the serverScript php file  you can do     profile viewer uid     POST  profile viewer uid     echo  profile viewer uid       prints 1   Note  in this example I used jQuery AJAX  which is quicker to implement  You can do it in pure js as well

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You will need to use JS to send the URL back with a variable in it such as  http   www site com index php uid 1  by using something like this in JS   window location href    index php uid 1     Then in the PHP code use   GET    somevar     GET  uid      puts the uid varialbe into  somevar

[php] How to get JavaScript variable value in PHP

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