$re = '@<drupal-entity[^>]+></drupal-entity><p> </p>@';
$str = '</p><drupal-entity data-view-mode="oembed_display"></drupal-entity><p><strong>Designer Crush:</strong></p><drupal-entity data-view-mode="oembed_display"></drupal-entity><p> </p>';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php