Drupal 8: Debug Database Query

DebugQuery.php

<?php

namespace Drupal\YOURNAMESPACE\Helper;

use Drupal\Core\Database\Query\SelectInterface;

class DebugQuery {

  /**
   * Debug a database query and print it out.
   *
   * @code
   * DebugQuery::debug($query);
   * @endcode
   *
   * @param \Drupal\Core\Database\Query\SelectInterface $query
   *   The query.
   * @param bool $replace_arguments
   *   Replaces the query placeholder with the arguments.
   */
  public static function printQuery(SelectInterface $query, $replace_placeholder = TRUE) {
    print self::debug($query, $replace_placeholder); 
  }

  /**
   * Debug a database query.
   *
   * @code
   * print(DebugQuery::debug($query));
   * @endcode
   * 
   * Or with devel installed:
   * @code
   * dsm(DebugQuery::debug($query));
   * @endcode
   *
   * @param \Drupal\Core\Database\Query\SelectInterface $query
   *   The query.
   * @param bool $replace_arguments
   *   Replaces the query placeholder with the arguments.
   *
   * @return string
   *   The query string.
   */
  public static function debug(SelectInterface $query, $replace_placeholder = TRUE) {
    $string = (string) $query;
    $arguments = $query->arguments();

    if ($replace_placeholder && !empty($arguments) && is_array($arguments)) {
      foreach ($arguments as $placeholder => &$value) {
        if (is_string($value)) {
          $value = "'$value'"; 
        }
      }

      $string = strtr($string, $arguments);
    }

    $string = str_replace(array('{', '}'), '', $string);
    
    return $string;
  }

}

function.php

<?php

/**
 * Debug a database query.
 *
 * @code
 * print(DebugQuery::debug($query));
 * @endcode
 * 
 * Or with devel installed:
 * @code
 * dsm(DebugQuery::debug($query));
 * @endcode
 *
 * @param \Drupal\Core\Database\Query\SelectInterface $query
 *   The query.
 * @param bool $replace_arguments
 *   Replaces the query placeholder with the arguments.
 *
 * @return string
 *   The query string.
 */
function debug_query($query, $replace_placeholder = TRUE) {
  $string = (string) $query;
  $arguments = $query->arguments();

  if ($replace_placeholder && !empty($arguments) && is_array($arguments)) {
    foreach ($arguments as $placeholder => &$value) {
      if (is_string($value)) {
        $value = "'$value'"; 
      }
    }

    $string = strtr($string, $arguments);
  }

  $string = str_replace(array('{', '}'), '', $string);
  
  return $string;
}