Simple HTML Output minifcation example

htmlMinification.php

<?php

/**
 * Minify HTML output (HTML)
 * 
 * How to use:
 * 
 * Call function using ob_start();
 * 
 * if(extension_loaded('zlib') && isset($_SERVER['HTTP_ACCEPT_ENCODING']) && strpos($_SERVER['HTTP_ACCEPT_ENCODING'], 'gzip') !== FALSE){
 *    ob_start('minify_output');
 * }

 * @param type $output
 * @return type
 */
function minify_output($output){
    ob_gzhandler();
    
    // Clean comments
    // Remove comments (non-MSIE conditionals)
    // Remove CSS comments
    // Clean Whitespace
    $regex_expression = array('{\s*<!--[^\[<>].*(?<!!)-->\s*}msU', '!/\*[^*]*\*+([^/][^*]*\*+)*/!i', '/<!--(.|s)*?-->/', '/\s{2,}/', '/(\r?\n)/');
    $arrayOutput = array('', '', '', '', '');

    $output =  preg_replace($regex_expression, $arrayOutput, $output);
    return $output;
}