[WP] HTML minify class WP_HTML_Compression

compress.php

<?php defined('ABSPATH') or header('Location: /');
/**
 * HTML document compression
 *
 * Clean and minify all markup
 * Wrap `<!--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 $strip_whitespace = true;  // May cause spacing issues within content
  protected $remove_cdata     = true;  // Remove CDATA within script tags
  protected $info_comment     = false; // Add custom comment to bottom of document
  protected $ignore_flag      = '<!--no compression-->'; // Comment used as a flag to skip minifying a section of markup
  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){
    $html = preg_replace('/\>\s+\</m', '><', $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){
      $strip   = $this->strip_whitespace;
      $tag     = (isset($token['tag'])) ? strtolower($token['tag']) : null;
      $content = $token[0];
      
      if(is_null($tag)){
        
        if(!empty($token['script']) ){
          
          if(!$overriding){
            $strip = $this->compress_js;
            $content = str_replace(array(' type="text/javascript"', " type='text/javascript'"), array('', ''), $content);
            if($this->remove_comments){
              $content = preg_replace('#^\s*// .+$#m', '', $content); // Removes inline JS comments
            }
            if($this->remove_cdata) {
              $content = str_replace(array('//<![CDATA[', '//]]>'), array('', ''), $content);
            }
          }
          
        }elseif(!empty($token['style'])){
          $strip = $this->compress_css;
          $content = str_replace(array(' type="text/css"', " type='text/css'"), array('', ''), $content);
          
        }elseif($content == $this->ignore_flag){
          $overriding = !$overriding;
          continue;
          
        }elseif($this->remove_comments){
          if(!$overriding && $raw_tag != 'textarea'){
            $content = preg_replace('#\s*<!--(?!\[if\s).*?-->\s*|(?<!\>)\n+(?=\<[^!])#s', '', $content); // Remove any HTML comments, except IE conditionals
          }
        }
        
      }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;    
            $content = preg_replace('#\s*(\w++(?<!\baction|\balt|\bcontent|\bsrc|\bvalue)="")#s', '$1', $content); // Remove any empty attributes no certain tags         
            $content = str_replace(' />', '>', $content); // Fix self closing tags
          }
        }
        
      }
      
      if($strip){
        if(!$overriding){
          $content = $this->remove_white_space($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 = preg_replace('/\s+/', ' ', $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');
}