protected function searchMenu()
	{
		$searchFields = array();

		/** @var AttributeBagInterface $objSessionBag */
		$objSessionBag = System::getContainer()->get('session')->getBag('contao_backend');

		$session = $objSessionBag->all();

		// Get search fields
		foreach ($GLOBALS['TL_DCA'][$this->strTable]['fields'] as $k=>$v)
		{
			if ($v['search'])
			{
				$searchFields[] = $k;
			}
		}

		// Return if there are no search fields
		if (empty($searchFields))
		{
			return '';
		}

		// Store search value in the current session
		if (Input::post('FORM_SUBMIT') == 'tl_filters')
		{
			$strField = Input::post('tl_field', true);
			$strKeyword = ltrim(Input::postRaw('tl_value'), '*');

			if ($strField && !\in_array($strField, $searchFields, true))
			{
				$strField = '';
				$strKeyword = '';
			}

			// Make sure the regular expression is valid
			if ($strField && $strKeyword)
			{
				try
				{
					$this->Database->prepare("SELECT * FROM " . $this->strTable . " WHERE " . Database::quoteIdentifier($strField) . " REGEXP ?")
								   ->limit(1)
								   ->execute($strKeyword);
				}
				catch (\Exception $e)
				{
					$strKeyword = '';
				}
			}

			$session['search'][$this->strTable]['field'] = $strField;
			$session['search'][$this->strTable]['value'] = $strKeyword;

			$objSessionBag->replace($session);
		}

		// Set the search value from the session
		elseif ($session['search'][$this->strTable]['value'] != '')
		{
			$strPattern = "CAST(%s AS CHAR) REGEXP ?";

			if (substr(Config::get('dbCollation'), -3) == '_ci')
			{
				$strPattern = "LOWER(CAST(%s AS CHAR)) REGEXP LOWER(?)";
			}

			$fld = $session['search'][$this->strTable]['field'];

			if (isset($GLOBALS['TL_DCA'][$this->strTable]['fields'][$fld]['foreignKey']))
			{
				list($t, $f) = explode('.', $GLOBALS['TL_DCA'][$this->strTable]['fields'][$fld]['foreignKey'], 2);
				$this->procedure[] = "(" . sprintf($strPattern, Database::quoteIdentifier($fld)) . " OR " . sprintf($strPattern, "(SELECT " . Database::quoteIdentifier($f) . " FROM $t WHERE $t.id=" . $this->strTable . "." . Database::quoteIdentifier($fld) . ")") . ")";
				$this->values[] = $session['search'][$this->strTable]['value'];
			}
			else
			{
				$this->procedure[] = sprintf($strPattern, Database::quoteIdentifier($fld));
			}

			$this->values[] = $session['search'][$this->strTable]['value'];
		}

		$options_sorter = array();

		foreach ($searchFields as $field)
		{
			$option_label = $field;

			if (isset($GLOBALS['TL_DCA'][$this->strTable]['fields'][$field]['label']))
			{
				$option_label = \is_array($GLOBALS['TL_DCA'][$this->strTable]['fields'][$field]['label']) ? $GLOBALS['TL_DCA'][$this->strTable]['fields'][$field]['label'][0] : $GLOBALS['TL_DCA'][$this->strTable]['fields'][$field]['label'];
			}
			elseif (isset($GLOBALS['TL_LANG']['MSC'][$field]))
			{
				$option_label = \is_array($GLOBALS['TL_LANG']['MSC'][$field]) ? $GLOBALS['TL_LANG']['MSC'][$field][0] : $GLOBALS['TL_LANG']['MSC'][$field];
			}

			$options_sorter[Utf8::toAscii($option_label).'_'.$field] = '  <option value="'.StringUtil::specialchars($field).'"'.(($field == $session['search'][$this->strTable]['field']) ? ' selected="selected"' : '').'>'.$option_label.'</option>';
		}

		// Sort by option values
		$options_sorter = natcaseksort($options_sorter);
		$active = ($session['search'][$this->strTable]['value'] != '') ? true : false;

		return '
<div class="tl_search tl_subpanel">
<strong>' . $GLOBALS['TL_LANG']['MSC']['search'] . ':</strong>
<select name="tl_field" class="tl_select' . ($active ? ' active' : '') . '">
'.implode("\n", $options_sorter).'
</select>
<span>=</span>
<input type="search" name="tl_value" class="tl_text' . ($active ? ' active' : '') . '" value="'.StringUtil::specialchars($session['search'][$this->strTable]['value']).'">
</div>';
	}
protected function searchMenu()
	{
		$searchFields = array();

		/** @var AttributeBagInterface $objSessionBag */
		$objSessionBag = System::getContainer()->get('session')->getBag('contao_backend');

		$session = $objSessionBag->all();

		// Get search fields
		foreach ($GLOBALS['TL_DCA'][$this->strTable]['fields'] as $k=>$v)
		{
			if ($v['search'])
			{
				$searchFields[] = $k;
			}
		}

		// Return if there are no search fields
		if (empty($searchFields))
		{
			return '';
		}

		// Store search value in the current session
		if (Input::post('FORM_SUBMIT') == 'tl_filters')
		{
			$strField = Input::post('tl_field', true);
			$strKeyword = ltrim(Input::postRaw('tl_value'), '*');

			if ($strField && !\in_array($strField, $searchFields, true))
			{
				$strField = '';
				$strKeyword = '';
			}

			// Make sure the regular expression is valid
			if ($strField && $strKeyword)
			{
				try
				{
					$this->Database->prepare("SELECT * FROM " . $this->strTable . " WHERE " . Database::quoteIdentifier($strField) . " REGEXP ?")
								   ->limit(1)
								   ->execute($strKeyword);
				}
				catch (\Exception $e)
				{
					$strKeyword = '';
				}
			}

			$session['search'][$this->strTable]['field'] = $strField;
			$session['search'][$this->strTable]['value'] = $strKeyword;

			$objSessionBag->replace($session);
		}

		// Set the search value from the session
		elseif ($session['search'][$this->strTable]['value'] != '')
		{
			$strPattern = "CAST(%s AS CHAR) REGEXP ?";

			if (substr(Config::get('dbCollation'), -3) == '_ci')
			{
				$strPattern = "LOWER(CAST(%s AS CHAR)) REGEXP LOWER(?)";
			}

			$fld = $session['search'][$this->strTable]['field'];

			if (isset($GLOBALS['TL_DCA'][$this->strTable]['fields'][$fld]['foreignKey']))
			{
				list($t, $f) = explode('.', $GLOBALS['TL_DCA'][$this->strTable]['fields'][$fld]['foreignKey'], 2);
				$this->procedure[] = "(" . sprintf($strPattern, Database::quoteIdentifier($fld)) . " OR " . sprintf($strPattern, "(SELECT " . Database::quoteIdentifier($f) . " FROM $t WHERE $t.id=" . $this->strTable . "." . Database::quoteIdentifier($fld) . ")") . ")";
				$this->values[] = $session['search'][$this->strTable]['value'];
			}
			else
			{
				$this->procedure[] = sprintf($strPattern, Database::quoteIdentifier($fld));
			}

			$this->values[] = $session['search'][$this->strTable]['value'];
		}

		$options_sorter = array();

		foreach ($searchFields as $field)
		{
			$option_label = $field;

			if (isset($GLOBALS['TL_DCA'][$this->strTable]['fields'][$field]['label']))
			{
				$option_label = \is_array($GLOBALS['TL_DCA'][$this->strTable]['fields'][$field]['label']) ? $GLOBALS['TL_DCA'][$this->strTable]['fields'][$field]['label'][0] : $GLOBALS['TL_DCA'][$this->strTable]['fields'][$field]['label'];
			}
			elseif (isset($GLOBALS['TL_LANG']['MSC'][$field]))
			{
				$option_label = \is_array($GLOBALS['TL_LANG']['MSC'][$field]) ? $GLOBALS['TL_LANG']['MSC'][$field][0] : $GLOBALS['TL_LANG']['MSC'][$field];
			}

			$options_sorter[Utf8::toAscii($option_label).'_'.$field] = '  <option value="'.StringUtil::specialchars($field).'"'.(($field == $session['search'][$this->strTable]['field']) ? ' selected="selected"' : '').'>'.$option_label.'</option>';
		}

		// Sort by option values
		$options_sorter = natcaseksort($options_sorter);
		$active = ($session['search'][$this->strTable]['value'] != '') ? true : false;

		return '
<div class="tl_search tl_subpanel">
<strong>' . $GLOBALS['TL_LANG']['MSC']['search'] . ':</strong>
<select name="tl_field" class="tl_select' . ($active ? ' active' : '') . '">
'.implode("\n", $options_sorter).'
</select>
<span>=</span>
<input type="search" name="tl_value" class="tl_text' . ($active ? ' active' : '') . '" value="'.StringUtil::specialchars($session['search'][$this->strTable]['value']).'">
</div>';
	}
Return a search form that allows to search results using regular expressions

@return string