wordpress, match keywords in content to other posts in the same website

$keyword_found = false;

foreach( $post_array as $post ){
  foreach( $post->content as $content_item ){
    foreach( $keywords as $keyword ){
      if( $content_item == $keyword ){
        $keyword_found == true;
      }
    }
  }
}

if( $keyword_found == true ){
  print 'content'
}