Contao\Input::postRaw PHP Method

    public static function postRaw($strKey)
    {
        $strCacheKey = 'postRaw';
        if (!isset(static::$arrCache[$strCacheKey][$strKey])) {
            $varValue = static::findPost($strKey);
            if ($varValue === null) {
                return $varValue;
            }
            $varValue = static::preserveBasicEntities($varValue);
            $varValue = static::xssClean($varValue);
            if (TL_MODE != 'BE') {
                $varValue = static::encodeInsertTags($varValue);
            }
            static::$arrCache[$strCacheKey][$strKey] = $varValue;
        }
        return static::$arrCache[$strCacheKey][$strKey];
    }

    /**
     * Return a search form that allows to search results using regular expressions
     *
     * @return string
     */
    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);
            $strKeyword = ltrim(\Input::postRaw('tl_value'), '*');
            // Make sure the regular expression is valid
            if ($strKeyword != '') {
                try {
                    $this->Database->prepare("SELECT * FROM " . $this->strTable . " WHERE " . $strField . " REGEXP ?")->limit(1)->execute($strKeyword);
                } catch (\Exception $e) {
                    $strKeyword = '';
                }
            }
            $session['search'][$this->strTable]['field'] = $strField;
            $session['search'][$this->strTable]['value'] = $strKeyword;
            $objSessionBag->replace($session);
        } 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']);
                $this->procedure[] = "(" . sprintf($strPattern, $fld) . " OR " . sprintf($strPattern, "(SELECT {$f} FROM {$t} WHERE {$t}.id={$this->strTable}.{$fld})") . ")";
                $this->values[] = $session['search'][$this->strTable]['value'];
            } else {
                $this->procedure[] = sprintf($strPattern, $fld);
            }
            $this->values[] = $session['search'][$this->strTable]['value'];
        }
        $options_sorter = array();
        foreach ($searchFields as $field) {
            $option_label = $GLOBALS['TL_DCA'][$this->strTable]['fields'][$field]['label'][0] ?: (is_array($GLOBALS['TL_LANG']['MSC'][$field]) ? $GLOBALS['TL_LANG']['MSC'][$field][0] : $GLOBALS['TL_LANG']['MSC'][$field]);
            $options_sorter[Utf8::toAscii($option_label) . '_' . $field] = '  <option value="' . specialchars($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="' . specialchars($session['search'][$this->strTable]['value']) . '">
</div>';
    }