/**
* Used to escape scalar or attach escape callable.
*
* @param scalar|callable $callable Scalar to escape or callable for escaping.
* @return string|null
*/
public static function escape($callable)
{
if ($callable === null) {
return Expression::_('NULL');
} else {
if (is_scalar($callable)) {
return static::$_escaper ? call_user_func(static::$_escaper, $callable) : $callable;
} else {
if (is_callable($callable)) {
static::$_escaper = $callable;
} else {
throw new \Exception("Given argument is not callable nor scalar.");
}
}
}
}