phpregexsubtractionblacklistcharacter-class

Regex Character Class Subtraction with PHP

I'm trying to match UK postcodes, using the pattern from http://interim.cabinetoffice.gov.uk/media/291370/bs7666-v2-0-xsd-PostCodeType.htm,

/^[A-Z]{1,2}[0-9R][0-9A-Z]? [0-9][A-Z-[CIKMOV]]{2}$/

I'm using this in PHP, but it doesn't match the valid postcode OL13 0EF. This postcode does match, however, when I remove the -[CIKMOV] character class subtraction.

I get the impression that I'm doing character class subtraction wrong in PHP. I'd be most grateful if anyone could correct my error.

Solution

  • Most of the regex flavours do not support character class subtraction. Instead you could use look-ahead assertion:

    /^[A-Z]{1,2}[0-9R][0-9A-Z]? [0-9](?!.?[CIKMOV])[A-Z]{2}$/