function parseUkPostcode($postcode) {

	$postcode = strtoupper(ereg_replace("[^A-Za-z0-9]", "", trim($postcode)));

	$lenght = strlen($postcode);
	
	if($lenght < 5 OR $lenght == 4){
		
		$regex = '/^([A-Z]{1,2})([0-9][0-9A-Z]?)$/';
		
		if (preg_match($regex, $postcode, $part)) { 
			
			$code = array(
		                 'full' 	=> $part[1] . $part[2],
		                 'area'     => $part[1],
		                 'district' => $part[2],
		                 'outer'    => $part[1] . $part[2],
		                 'sector'   => NULL,
		                 'walk'     => NULL,
		                 'inner'    => NULL
		                 );		 
		
		}else{
			
			$code = NULL;
			
		}
		
	}else{
		
		$regex = '/^([A-Z]{1,2})([0-9][0-9A-Z]?)\s*([0-9])([A-Z]{2})$/';
		
		if (preg_match($regex, $postcode, $part)) { 
			
			$code = array(
		                 'full' => $part[1].$part[2].' '.$part[3].$part[4],
		                 'area'     => $part[1],
		                 'district' => $part[2],
		                 'outer'    => $part[1] . $part[2],
		                 'sector'   => $part[3],
		                 'walk'     => $part[4],
		                 'inner'    => $part[3] . $part[4]
		                 );		 
		
		}else{
			
			$code = NULL;
			
		}
	}
   return $code;                
}

This function can validate and parse UK postcode like SW1A 1AA in to formated array.

UK postcode parser

regex, php, array

PHP