src/Resources/BaseDbTableResource.php
public static function interpretFilterValue($value)
    {
        // all other data types besides strings, just return
        if (!is_string($value) || empty($value)) {
            return $value;
        }

        $end = strlen($value) - 1;
        // filter string values should be wrapped in matching quotes
        if (((0 === strpos($value, '"')) && ($end === strrpos($value, '"'))) ||
            ((0 === strpos($value, "'")) && ($end === strrpos($value, "'")))
        ) {
            return substr($value, 1, $end - 1);
        }

        // check for boolean or null values
        switch (strtolower($value)) {
            case 'true':
                return true;
            case 'false':
                return false;
            case 'null':
                return null;
        }

        if (is_numeric($value)) {
            return $value + 0; // trick to get int or float
        }

        // the rest should be lookup keys, or plain strings
        Session::replaceLookups($value);

        return $value;
    }
public static function interpretFilterValue($value)
    {
        // all other data types besides strings, just return
        if (!is_string($value) || empty($value)) {
            return $value;
        }

        $end = strlen($value) - 1;
        // filter string values should be wrapped in matching quotes
        if (((0 === strpos($value, '"')) && ($end === strrpos($value, '"'))) ||
            ((0 === strpos($value, "'")) && ($end === strrpos($value, "'")))
        ) {
            return substr($value, 1, $end - 1);
        }

        // check for boolean or null values
        switch (strtolower($value)) {
            case 'true':
                return true;
            case 'false':
                return false;
            case 'null':
                return null;
        }

        if (is_numeric($value)) {
            return $value + 0; // trick to get int or float
        }

        // the rest should be lookup keys, or plain strings
        Session::replaceLookups($value);

        return $value;
    }
@param $value

@return bool|int|null|string