passing variables to second php when using multiple forms

You can use sessions for this.

As an example, I've set up 3 different bodies of code. This method is based on entering a username and password.

It doesn't matter what you enter, it won't do anything but post the variables on all subsequent pages.

This is to give you a general feel of how sessions work and how variables can be used throughout different pages.

Page 1

<?php
ob_start();
session_start();

    if(isset($_POST['submit'])){

    $_SESSION['myusername'] = $_POST['myusername'];
    $_SESSION['mypassword'] = $_POST['mypassword'];

    echo $_SESSION['myusername'];
    echo "<br>";
    echo $_SESSION['mypassword'];

} // isset submit

ob_end_flush();
?>

<form action="" method="post">

Username: 
<input type="text" name="myusername">
<br>
Password: 
<input type="text" name="mypassword">
<br>
<input type="submit" name="submit" value="Submit">
</form>

<br><br>
<a href="check_page2.php">check page 2</a>

Page 2 (check_page2.php)

<?php
    session_start();
    if (isset( $_SESSION['myusername']) && isset( $_SESSION['mypassword']) ){

    $myusername = $_SESSION['myusername'];
    $mypassword = $_SESSION['mypassword'];

    echo $myusername;
    echo "<br>";
    echo $mypassword;
    }
?>

<br><br>
<a href="check_page3.php">check again on page 3</a>

Page 3 (check_page3.php)

<?php
    session_start();
    if (isset( $_SESSION['myusername']) && isset( $_SESSION['mypassword']) ){

    $myusername = $_SESSION['myusername'];
    $mypassword = $_SESSION['mypassword'];

    echo $myusername;
    echo "<br>";
    echo $mypassword;
}
?>

You could even use a session variable with jQuery.

Just add: (to check_page3.php) after the closing ?> PHP tag:

<a href="check_jquery.php">check jQuery variable in source</a>

And inside that, you can use: (check_jquery.php)

which will show the username variable inside the HTML source. (as an example)

<?php
session_start();
if (isset( $_SESSION['myusername']) && isset( $_SESSION['mypassword']) ){

$myusername = $_SESSION['myusername'];
$mypassword = $_SESSION['mypassword'];

echo $myusername;
echo "<br>";
echo $mypassword;
}
?>

<script src="http://code.jquery.com/jquery-1.9.1.js"></script>
<script>
    $(document).ready(function(){
var usersession = "<?php echo $_SESSION['myusername']; ?>";

// alert (usersession);

    });
</script>

Footnotes:

Generally using type="password" would need to be used for:

<input type="text" name="mypassword"> but this was just an example.

The actual syntax would be:

<input type="password" name="mypassword"> in order to mask an entered password.