<p>Where can I find a free, lightweight YUI-like compressor for PHP?</p>

<p>I am sure it will decrease the file size but will compressing PHP code boost its performance?</p>

<p>Is this the same thing as an obfuscator?</p>

There is a product called PHP Encoder by ionCube (
http://www.ioncube.com/sa_encoder.php
) which is enterprise grade compression and obfuscater.
PHP Encoder is a PHP extension to create and run compiled bytecodes for accelerated runtime performance and maximum security.
It will shrink the file size, and speed up runtime because the code is already partially compiled