I would use $ _POST twice in one page - php

Question

I have a site where I make a payment, a bill is created through it, but the problem is that I can not use $ _POST twice in one, and this example:
<? if (isset($_POST['submit'])) { ?>
<form action="" method="POST" >
<input name="invoice" value="" type="text" />
<input name="pay" value="Pay Now" type="submit" />
</form>
<? } if (isset($_POST['pay'])) {
// MY QUERY HERE
// HEADERS HERE
} else { ?>
<form action="" method="POST" >
<input name="info" value="" type="text" />
<input name="submit" value="Submit" type="submit" />
</form>
<? } ?>

Answer 1

Try this.
Kindly check the code for comment.
<?
if (isset($_POST['submit'])) {
$info = $_POST['info'];
// use echo to display second form
echo '
<form action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]);?>" method="POST" >
<!-- // Note the action value, it's for post back. This allow you to post back to the current page -->
<!-- This is to keep the record passed from the first form -->
<input name="info" value="'. $info .'" type="hidden" />
<input name="invoice" value="" type="text" />
<input name="pay" value="Pay Now" type="submit" />
</form>';
} else if (isset($_POST['pay'])) {
// MY QUERY HERE
} else {
// Note the action value, it's for post back. This allow you to post back to the current page
<form action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]);?>" method="POST" >
<input name="info" value="" type="text" />
<input name="submit" value="Submit" type="submit" />
</form>
}
?>

Answer 2

Not the prettiest way to do this but to achieve your result try this...
<?php if (isset($_POST['submit'])) { ?>
<form action="" method="POST" >
<input name="invoice" value="" type="text" />
<input name="pay" value="Pay Now" type="submit" />
</form>
<?php } elseif (isset($_POST['pay'])) {
// Perform query here
} else { ?>
<form action="" method="POST" >
<input name="info" value="" type="text" />
<input name="submit" value="Submit" type="submit" />
</form>
<?php } ?>