Webpage favourite button

<?php
/*
* Snippet add button on page to save current document to extended user field or remove it.
* Requirements: Login Extra, created extended field for each user: Favorite Page, Change redirect page for not logged user, set max value
*
* Call on page:
* [[!saveFavorite]]
* <form action="[[~[[*id]]]]" method="post">
*   <input type="hidden" name="favorite_page" value="[[*id]]" />
*   <input type="submit" name="fav_submit" [[+FavPH]] />
* </form>
*/
$max = 14; //maximum allowed favorites
$modx->setPlaceholder('FavPH','class="fav-star" title="Please log in" value="Login to add to favorites" '); //initialize default button value
$id = $modx->resource->get('id'); //current id
$sent_id = (int) $_POST['favorite_page'];       //posted id of saved page

if ($modx->user->hasSessionContext($modx->context->get('key'))) {   // if logged in
 
    // Get the user's extended fields
    $profile = $modx->user->getOne('Profile');
    $fields = $profile->get('extended');
  	$fav_field = explode(",", $fields['Favorite Page']); // change string to array
  	    
    if ((count($fav_field) > $max) and ($sent_id == $id)) {      //if more then max value
      $modx->setPlaceholder('FavPH','class="fav-star" title="Add to Favorites" value="Add to Favorites" '); // change placeholder text
      return "Max amount of " . $max . " pages in favorites reached!";  // do not add new value, return warning
    }
    if (in_array($id, $fav_field)) {  // if found in array 
	      if ($sent_id == $id) {   // if clicked to form button 
	        foreach (array_keys($fav_field, $sent_id) as $key) unset($fav_field[$key]);   // page is removed from favorites
          $modx->setPlaceholder('FavPH','class="fav-star" title="Add to Favorites" value="Add to Favorites" '); // change placeholder text
          $fields['Favorite Page'] = implode(",", $fav_field); //put the rest back in extended field
		      $profile->set('extended',$fields);
          $profile->save();
		      return; 
          
		    }           // change placeholder text if already in field but button not clicked
	      $modx->setPlaceholder('FavPH',' class="fav-star-selected" title="Remove from Favorites" value="Remove from Favorites" '); 
	      return;
     }
	   
     if (empty($sent_id)) {   //document not yet added to fav and button not clicked
       $modx->setPlaceholder('FavPH',' class="fav-star" title="Add to Favorites" value="Add to Favorites"');
	     return; 
     }
	   else array_push($fav_field, $sent_id); //document not yet added to fav but button IS clicked, add new id to extended field
	   $fields['Favorite Page'] = implode(",", $fav_field); //convert array to string
	   $profile->set('extended',$fields);
     $profile->save();
	   $modx->setPlaceholder('FavPH',' class="fav-star-selected" title="Remove from Favorites" value="Remove from Favorites"');//change placehodler
     return;
}

if ($sent_id == $id) {           //if not logged in redirect to login page (57) - change it!
  $url = $modx->makeUrl(57);
  $modx->sendRedirect($url);
  }
return;

[[!Profile]]
[[!getResources? &parents=`-1` &resources=`[[+Favorite Page]]` &tpl=`myRowTpl`]]

<label for="Favorite Page">Favorite Page:
            <span class="error">[[+error.Favorite Page]]</span>
        </label>
        <input type="text" name="Favorite Page" id="Favorite Page" value="[[+Favorite Page]]" />

<input type="hidden" name="Favorite Page" />