Assign a Javascript variable to PHP variable

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When working with PHP and JavaScript together, there are times when you need to pass values from JavaScript to PHP. This can be done by assigning a JavaScript variable to a PHP variable. In this post, We will explain different methods to do that.

<script> document.cookie = "js_var_value = " + localStorage.value </script>
<?php
    $php_var_val= $_COOKIE['js_var_value'];
    echo $php_var_val;
?>

Why do we assign a Javascript variable to a PHP variable?

There are many reasons why one might want to assign a Javascript variable to a PHP variable. Some possible reasons include:

-To pass data from Javascript to PHP (for example, to use PHP to process or store data that was entered into a form via Javascript)

-To make use of PHP's built-in functions and libraries from within Javascript

-To take advantage of PHP's faster execution speed when working with large data sets or complex algorithms.

Use document.cookie and $_COOKIE to assign a JS variable to a PHP variable

The document.cookie is used to store cookies in javascript and $_COOKIE is a PHP superglobal variable that is used to access cookies. We will use document.cookie to store javascript variable value to a cookie and access it in PHP using $_COOKIE.

<script>
    var user_name = "Rohit";
    document.cookie = "name = " + user_name;
</script>

<?php
    $name= $_COOKIE['name'];
    echo $name;
?>

In the above code example:

We have a Javascript variable named user_name that contains a string value.
We are creating a cookie named name in Javascript and assigning it the user_name variable value.
In the PHP code, we are getting the cookie using $_COOKIE['name'].

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<script>
            document.cookie= "h1 ="+screen.height;
            document.cookie= "h2 ="+window.innerHeight;
            document.cookie= "w1 ="+screen.width;
            document.cookie= "w2 ="+window.innerWidth;
            document.cookie= "c ="+screen.colorDepth;
            document.cookie= "cookies ="+navigator.cookieEnabled;
            document.cookie= "lang ="+navigator.language;
            document.cookie= "java ="+navigator.javaEnabled();
            document.writeln("<br>Resolution is: " + screen.height + ";" + screen.width + "<br>Window resolution is: " + window.innerHeight + ";" + window.innerWidth + "<br>Ilosc kolorów ekranu: " + screen.colorDepth + "bit<br>" + "Ciasteczka: " + navigator.cookieEnabled + "<br>Jezyk przegladarki: " + navigator.language + "<br>Java: " + navigator.javaEnabled());
            </script>

$h1 = $_COOKIE['h1'];
$h2 = $_COOKIE['h2'];
$w1 = $_COOKIE['w1'];
$w2 = $_COOKIE['w2'];
$c = $_COOKIE['c'];
$cookies = $_COOKIE['cookies'];
$lang = $_COOKIE['lang'];
$java = $_COOKIE['java'];

The first time you log in it doesn't work. If you reload the page everything is fine. This is because php will execute first only then the javascript.

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