CODEWITHSUNDEEP
regexregex-lookarounds
eComEvo
eComEvo

Reputation: 12551

Negative look behind with variable length match before it

I'm trying to extract a lone # on the end of addresses, but only if not after certain designations.

Here is the regex I am testing:

/(?<!apt|appt|appartment|ste|suite|box)[,.]? ?# ?([0-9]+)$/i

The regex should fail in this case:

123 W Somewhere St Apt # 321

The regex should find a match in this:

123 W Somewhere St # 321

However, it matches both of the above.

I found that if I change [,.]? ?# ? to simply # then it works.

However, that means that simply removing a space or adding a period to the address will throw it off.

How do I get my negative look-behind to work and allow my regex to remain flexible in this instance?

Implemented in PHP 5.3.

Upvotes: 1

Views: 100

Answers (1)

Casimir et Hippolyte
Casimir et Hippolyte

Reputation: 89547

You can't use a lookbehind in this situation (with optional content after), but you can use this alternative:

/(?!\b(?:apt|appt|appartment|ste|suite|box))\b\w+[,.]? ?# ?\K[0-9]+/i

\K reset all the match before.

Upvotes: 1

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