10.7.1 I would like to write a generic PHP script that can handle data coming from any form. How do I know which POST method variables are available?

PHP offers many predefined variables , like the superglobal $_POST . You may loop through $_POST as it's an associate array of all POSTed values. For example, let's simply loop through it with foreach , check for empty values, and print them out.

<?php
$empty = $post = array();
foreach ($_POST as $varname => $varvalue) {
    if (empty($varvalue)) {
        $empty[$varname] = $varvalue;
    } else {
        $post[$varname] = $varvalue;
    }
}

print "<pre>";
if (empty($empty)) {
    print "None of the POSTed values are empty, posted:\n";
    var_dump($post);
} else {
    print "We have " . count($empty) . " empty values\n";
    print "Posted:\n"; var_dump($post);
    print "Empty:\n";  var_dump($empty);
    exit;
}
?>