Is there any method user can provide a variable to Serialized PHP array ? 

I tried $_SESSION, $GLOBALS that are preset in functions.php but nothing works. 

<?php
session_id("Test_Session");
session_start();
$var1 = $_SESSION["USER"];
$var1 = $GLOBAL["USER"];
$data[] = array("Name" => $var1, "Age" => "21");
echo serialize($data);
?>

Any feedback / suggestion would be very appreciated. 

Aleksandar:

Thanks for your patients and apologize for my lack of knowledge. But let me follow up with your suggestion (https://tmsplugins.ticksy.com/ticket/2371194/). Here is a page with WP one form and one Serialized PHP array table as attached snapshot. I need to pass one variable (s) from from to the PHP file. 

//front-end form

function mf_s() {

    $output = '<form action="' . $_PHP_SELF . '"'.' method="GET"> 
         S<input type="text" name="s"/>  <input type="submit" /> </form>';
    return $output;
}
add_shortcode( 'mf-s', 'mf_s' );

//Serialized PHP File: http://..../test_table.php

<?php

$s = "John"; //Need to GET value 's' from form
$data[] = array("Name" => $s, "Age" => "21");
echo serialize($data);

?>

Would you please elaborate more about statements and how to use 'apply_filters' ?

"...pack the URL in the hook, with GET parameters you receive from front-end"

$url = apply_filters('wpdatatables_filter_url_php_array', $tableData->content, $this->_wpId); 
$serialized_content = apply_filters('wpdatatables_filter_serialized', WDTTools::curlGetData($url), $this->_wpId);

Many thanks for your consideration and input again. 

Thanks for your information.