"Invalid type given. String expected", self::NOT_HEX => "The input contains non-hexadecimal characters", ); /** * Returns true if and only if $value contains only hexadecimal digit characters * * @param string $value * @return bool */ public function isValid($value) { if (!is_string($value) && !is_int($value)) { $this->error(self::INVALID); return false; } $this->setValue($value); if (!ctype_xdigit((string) $value)) { $this->error(self::NOT_HEX); return false; } return true; } }