Bits of Wisdom

Using an external Programm do do rewriting – in fact it can do anything depending on the request.

First a non-mentioned fact: if you use an external rewriting program  apache will spawn it as a child process. Yes, a deamon child spawned by mod_rewrite. Be shure to know what you do, otherwise you’ll do more harm than good.

First a simple rewrite Statement

RewriteEngine On
# define the rewrite map – videoMap will be spawned and used by rewrite rules. php-win does not open a window
RewriteMap videoMap “prg:c:/path/php-win.exe -c E:/path/to/php.ini/ E:/path/external_rewriteMap.php”

# match for /video/v= and throw anything after v= into the daemon child
RewriteRule ^/video/v=(.*) /vardump.php?param=${videoMap:$1} [NC]

# RewriteLock file is needed for process communication
RewriteLock rewriteLockFile.txt

The PHP file for it

<?php

// HERE BE DRAGONS
// as php runs as daemon, NEVER exit(), and note that input comes from STDIN as we are piping

while($input = trim(fgets(STDIN, 1024))) {
if ($input) {
fputs(STDOUT, decode($input) ); // IMPORTANT: write out result to STDOUT
}
fputs(STDOUT, “\n” ); // end processing for this line with linebreak
flush(); // flush sends the result to STDOUT, this is very important to, no buffering
}

function decode($encoded) {
// some code to decode encrypted request parameters
}

?>

Pitfalls for the php: if your php deamon exits, your rewritemap will return nothing. Make shure apache has a php child. Testing is a pain as you can use $argv[] while writing your php, but you need STDIN in the apache version. Make shure you pass the correct php ini when spawning the php process (-c path/to/php.ini/ )