Using a RewriteRule in Wordpress (It's set up, just not working).

Hey guys,

I've been pulling my hair out over this all night. My goal is to change this:

/review/reference/vocabulary/by-alphabet/a/
into (for now, as a test)
/temp/urlcheck.php?myvar=a

where "a" could be any letter or word.

So far, I've learned to put this into my functions page:

// Mod_rewrite stuff
add_action( 'init', 'wpse12708_init' );
function wpse12708_init()
{
    global $wp_rewrite;
    $wp_rewrite->add_external_rule('/review/reference/vocabulary/by-alphabet/([a-zA-Z_]+)/$', 'temp/urlcheck\.php?myvar=$1' );
}

PHP:

Which, after flushing the rewrites, puts this into my htaccess file:

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteRule ^/review/reference/vocabulary/by-alphabet/([a-zA-Z_]+)/$ /temp/urlcheck\.php?myvar=$1 [QSA,L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

# END WordPress

Code (markup):

I also tried it without escaping the period of "urlcheck.php", with no change. When I load up the URL:

/review/reference/vocabulary/by-alphabet/a/

It actually redirects to the post with the lowest id (/textbook/introduction/a-brief-history-of-greek/). I have no idea of where to look next. I don't think there are any plugins messing around with it, as I disabled all of my plugins, and still no luck.

The "urlcheck.php" page is simple, just to test this (I tested this, it's working fine):

<?php
define('WP_USE_THEMES', false);
require('../wp-load.php');

$currenturl = $_SERVER['REQUEST_URI'];
echo "Current url: $currenturl<br><br>";

print_r($_POST);
var_dump($_GET);

?>

PHP:

Any help would be amazing. I don't know what I'm doing with Apache .
Thanks!

P.S. As a side note, I did try a much simpler rewrite (/google.html -> google.com, to paraphrase it), and that worked just fine, so that shouldn't be the issue .