[WP] Wordpress - Clean and minify all markup

compress.php

<?php defined('ABSPATH') or header('Location: /');
/**
 * HTML document compression
 *
 * Clean and minify all markup
 * Wrap `<!--wp-html-compression no compression-->` to skip over content
 */
 
class WP_HTML_Compression {
  protected $compress_css    = true;  // Compress all inline styles
  protected $compress_js     = true;  // May cause issues if inline js contains single line `//` comments
  protected $remove_comments = true;  // Remove all html comments
  protected $tag_whitespace  = false; // May cause spacing issues within content
  protected $info_comment    = false; // Add custom comment to bottom of document
  protected $force_relative  = false; // May break canonical tags (since they need to be absolute)
  protected $html;
  
  
  /**
   * Construct
   */
  public function __construct($html){
    if(!empty($html)){
      $this->parse_html($html);
    }
  }
  
  
  /**
   * Markup to string
   */
  public function __toString(){
    if(is_null($this->html)) {
      return 'NULL';
    }
    
    return $this->html;
  }
  
  
  /**
   * Add comment
   */
  protected function bottom_comment($raw, $compressed){
    return '';
  }
  
  
  /**
   * Minify markup
   */
  protected function minify_html($html){
    $pattern = '/<(?<script>script).*?<\/script\s*>|<(?<style>style).*?<\/style\s*>|<!(?<comment>--).*?-->|<(?<tag>[\/\w.:-]*)(?:".*?"|\'.*?\'|[^\'">]+)*>|(?<text>((<[^!\/\w.:-])?[^<]*)+)|/si';
    preg_match_all($pattern, $html, $matches, PREG_SET_ORDER);
    
    $overriding = false;
    $raw_tag    = false;
    $html       = '';
    
    foreach ($matches as $token){
      $tag     = (isset($token['tag'])) ? strtolower($token['tag']) : null;
      $content = $token[0];
      
      if(is_null($tag)){
        if(!empty($token['script']) ){
          if(!$overriding){
            $strip = $this->compress_js;
          }
        }elseif( !empty($token['style']) ){
          $strip = $this->compress_css;
        }elseif($content == '<!--wp-html-compression no compression-->'){
          $overriding = !$overriding;
          // Don't print the comment
          continue;
        }elseif($this->remove_comments){
          if(!$overriding && $raw_tag != 'textarea'){
            // Remove any HTML comments, except MSIE conditional comments
            $content = preg_replace('/<!--(?!\s*(?:\[if [^\]]+]|<!|>))(?:(?!-->).)*-->/s', '', $content);
          }
        }
      }else{
        if($tag == 'pre' || $tag == 'textarea'){
          $raw_tag = $tag;
        }elseif($tag == '/pre' || $tag == '/textarea'){
          $raw_tag = false;
        }else{
          if($raw_tag || $overriding){
            $strip = false;
          }else{
            $strip = true;
            // Remove any empty attributes, except: action, alt, content, src or value
            $content = preg_replace('/(\s+)(\w++(?<!\baction|\balt|\bcontent|\bsrc|\bvalue)="")/', '$1', $content);
            // Remove any space before the end of self-closing XHTML tags, javaScript excluded
            $content = str_replace(' />', '>', $content);
            
            if($this->tag_whitespace) {
              $html = str_replace('> <', '><', $html);
            }
          }
        }
      }
      
      if($strip){
        $content = $this->remove_white_space($content);
        if($this->force_relative) {
          $content = $this->relative_urls($content);
        }
      }
      
      $html .= $content;
    }
    
    return $html;
  }
    

  /**
   * Parse markup
   */
  public function parse_html($html){
    $this->html = $this->minify_html($html);
    if($this->info_comment){
      $this->html .= "\n" . $this->bottom_comment($html, $this->html);
    }
  }
  
  
  /**
   * Remove white space
   */
  protected function remove_white_space($str){
    $str = str_replace("\t", ' ', $str);
    $str = str_replace("\n",  '', $str);
    $str = str_replace("\r",  '', $str);  
    while(stristr($str, '  ')){
      $str = str_replace('  ', ' ', $str);
    }
    
    return $str;
  }
  
  
  /**
   * Make relative URLs
   */
  protected function relative_urls($str){
    $str = str_replace(home_url(), '', $str);
    
    return $str;
  }
}


// Start compression
function wp_html_compression_start(){
  ob_start('wp_html_compression_finish');
}

// Finish compression
function wp_html_compression_finish($html){
  return new WP_HTML_Compression($html);
}

// Run class
if(!is_admin() && !is_user_logged_in() && !is_feed()){
  add_action('get_header', 'wp_html_compression_start');
}