PHP-based compression of HTML & CSS (doesn't compress whitespace in <pre> elements)

.htaccess

# compress the code
php_value auto_prepend_file ./prepend.php
php_value auto_append_file ./append.php

append.php

<?php

/* -----------------------------------------------------------------------------
 * Function: tidy_up( $buffer )
 * Purpose:  Clean up the markup
 * ---------------------------------------------------------------------------*/
function tidy_up( $buffer )
{
	# remove extra paragraphs
	$buffer = preg_replace( '/<p><\/p>/', '', $buffer );
	return $buffer;
}

/* -----------------------------------------------------------------------------
 * Function: mobilize( $buffer )
 * Purpose:  Compresses HTML for mobile delivery
 * ---------------------------------------------------------------------------*/
function mobilize( $buffer )
{
	$chunks = preg_split( '/(<pre.*?\/pre>)/ms', $buffer, -1, PREG_SPLIT_DELIM_CAPTURE );
	$buffer = '';
	foreach ( $chunks as $c )
	{
		if ( strpos( $c, '<pre' ) !== 0 )
		{
			# remove new lines & tabs
			$c = preg_replace( '/[\\n\\r\\t]+/', ' ', $c );
			# remove extra whitespace
			$c = preg_replace( '/\\s{2,}/', ' ', $c );
			# remove inter-tag whitespace
			$c = preg_replace( '/>\\s</', '><', $c );
			# remove CSS & JS comments
			$c = preg_replace( '/\\/\\*.*?\\*\\//i', '', $c );
		}
		$buffer .= $c;
	}
	return $buffer;
}

$buffer = ob_get_clean();

# don't compress JS files this way (some aren't ready for it)
if ( preg_match( "/\.js/", $_SERVER['REQUEST_URI'] ) === 0 )
{
	echo mobilize( tidy_up( $buffer ) );
}
else
{
	# you could use YUI compressor here
	echo $buffer;
}

?>

prepend.php

<?php ob_start(); ?>