PHP- Postcode validation function

The PHP function below checks to see if a string is a valid UK postcode. If the string is valid, the function will return true.

			//UK postcode validation check
			function isPostcodeValid($postcode)
				//remove all whitespace
				$postcode = preg_replace('/\s/', '', $postcode);

				//make uppercase
				$postcode = strtoupper($postcode);

					|| preg_match("/^[A-Z]{1,2}[0-9]{1}[A-Z]{1}[0-9]{1}[A-Z]{2}$/",$postcode)
					|| preg_match("/^GIR0[A-Z]{2}$/",$postcode))
					return true;
					return false;

If you have any suggestions to improve the code, please contact me and share your version.