I wrote database queries some time ago and now I would like to improve them.

But something I do wrong and i need help.

    class tags{

       private $wpdb;

      public function __construct(){

         global $wpdb; 
         global $table; 

        $this->wpdb = $wpdb; 

        $table = 'tags'; 
        $this->table_tags = $table;


        public function some(){

        // If I delete the value after the decimal point then it does not work. Is correct query and what use this query witch "WHERE"?

    $how_much = $this->wpdb->get_var($this->wpdb->prepare("SELECT COUNT(*) FROM `".$this->table_tags."`", $this->table_tags));           


        public function some2(){

           //here i need display some, work but I do this correct?

          $tags = $this->wpdb->get_results($this->wpdb->prepare("SELECT * FROM `".$this->table_tags."` ORDER BY id DESC LIMIT %d, %d", $from, $in_site), ARRAY_A);


        public function some3(){

        // here i want add some, work too

      $data  = array( 'name' => $name );

      $data2 = '%s';

      $this->wpdb->query($this->wpdb->prepare(" INSERT INTO `".$this->table_tags."` (`name`) VALUES (".$data2.") ", $data ));


    public function other(){

          // is correct? delete

              $this->wpdb->delete($this->table_tags, array('id' => $id));

         // and update

              $this->wpdb->update( $this->table_tags, array( 'name' => $name ), array( 'id' => $id )); 



And here question.

In $wpdb->delete and $wpdb->update it is not used prepare() and query() ?

  • I should use prepare() to all database operations ?
    – Jaron
    Apr 21, 2019 at 15:33

1 Answer 1


You should use prepare only when you're using SQL query - this function takes query and params and returns a safe SQL query filled with given params.

Its result is a SQL query. So you can (and should) use it whenever you're creating a SQL query and put some params in it.

With $wpdb->delete or $wpdb->update you don't create any string containing SQL query - both these functions are taking only params and the create and run the queries for you - so there is no need for preparing.

If you use $wpdb->insert, then you also don't have to prepare - there is nothing to be prepared.

But if you insert with raw SQL, as you do in your code, then yes - you should always prepare such query.

  • I always use $name= trim(sanitize_text_field($_POST['name']));
    – Jaron
    Apr 21, 2019 at 15:52
  • I still must use prepare always?
    – Jaron
    Apr 21, 2019 at 16:01
  • sanitize_text_field (developer.wordpress.org/reference/functions/sanitize_text_field) is not a solution - it doesn’t make given string sagę for DB queries. So if you’re usune it for escaping DB queries, then you use it incorrectly. Apr 21, 2019 at 16:06
  • I use it alwyas before run query, prepare values for query
    – Jaron
    Apr 21, 2019 at 16:10
  • @polyman so you’re doing it incorrectly and misuse this function - it does not escape values and does not prepare them for use in SQL queries (for example it doesn’t do anything with quotes; and it’s not meant to). On the other hand it does some things that not always are necessary (for example it strips tags and line breaks). Apr 21, 2019 at 16:14

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