get_post_meta2.php

<?php
/**
 * This function retrieves post meta using a custom $wpdb query. There are two reasons for this approach.
 *  1. When doing get_post_meta to query all the meta keys it returns an array or array
 *  2. This function also queries for LIKE fields. i.e, get_post_meta2(1, 'first_name, last_name, hobby_%')
 *
 * TODO: distinct meta_key, meta_value
 * 
 */

/**
 * Retrieves post meta field(s) for the given post ID.
 * 
 * @param  int                  $id   Post ID
 * @param  boolean|string|array $keys array or a comma separated meta_key string
 * @return array
 */
function get_post_meta2($id, $keys = false) {

  global $wpdb;

  if ( $keys && is_string($keys) ) {

    $keys = array_map(function($n) {

      return trim($n);

    }, explode(',', $keys));

  }

  $fields = "meta_key 'key', meta_value 'val'";

  $query = "SELECT {$fields} FROM {$wpdb->postmeta} WHERE post_id = {$id}";

  if ( is_array($keys) ) {

    $query .= " AND (";

    foreach ($keys as $k => $key) {

      $first_char = substr($key, 0, 1);
      $last_char = substr($key, -1);

      if ($first_char == '%' || $last_char == '%') {

        $operator = 'LIKE';

      } else {

        $operator = '=';

      }

      $query .= "meta_key " . $operator . " '" . $key . "'";

      if ( $k == count($keys) - 1 ) {

        $query .= ")";

      } else {

        $query .= " OR ";

      }

    }

  }

  $query .= " ORDER BY meta_id DESC";

  $results = $wpdb->get_results($query, ARRAY_A);
  $rows = array();

  foreach ($results as $result) {

    $rows[$result['key']] = $result['val'];

  }

  return $rows;

}