Session variable not maintaining value

//Check against CSFR here
            $key = md5(uniqid(rand(), TRUE));
            //$k开发者_如何学Cey = "234"; //using this works but not the idea
            $_SESSION['key'] = $key;


//form
<form method="post" action="<?php echo HTTPF; ?>/complete_reg">
        <p>
            <label>
                <b>Email address:</b><br />
                <input type="text" id="user_email" name="user_email" value="" class="register_email" onblur='$("#checkid").html("Please wait..."); $.get("er_checkuser.php",{ cmd: "check", check_key: $("#check_key").val(), user: $("#user_email").val() } ,function(data){  $("#checkid").html(data); });' />
            </label>
            <input type="hidden" id="check_key" name="check_key" value="<?php echo $key; ?>" />
            <span style="color:red; font: bold 12px verdana; " id="checkid" ></span>

        </p>

//calling page
//er_checkuser.php
foreach($_GET as $key => $value) {
    $get[$key] = filter($value);
}

//For some reasons I don't know why the values are not the same but they should be
if ($get['check_key'] == $_SESSION['key'])

{

    echo $_SESSION['key'];
    echo "<br>";
    echo $get['check_key'];
}

Ah I think I know where the problem is: you create a new key on every page reload. So you also create a new key when submitting the form.

What you should do is:

if(!isset($_GET['check_key']) {
    $key = md5(uniqid(rand(), TRUE));
    $_SESSION['key'] = $key;
}

Do you call session_start() before using the $_SESSION array?

You should call session_start() at the top of your php script or else I won't work.

session_start() creates a session or resumes the current one based on a session identifier passed via a GET or POST request, or passed via a cookie.

Maybe you can watch this video from nettuts to learn how to create login system, which uses sessions.