Question

I’m trying to parse product names that have multiple abbreviates for sizes. For example, medium can be

m, medium, med

I tried a simple

preg_match('/m|medium|med/i',$prod_name,$matches);

which works fine for ‘product m xyz’. However, when I try ‘product s/m abc’ I’m getting a false-positive match.
I also tried

preg_match('/\bm\b|\bmedium\b|\bmed\b/i',$prod_name,$matches);

to force it to be found in a word, but the m in s/m is still being matched. I’m assuming this is due to the engine treating ‘/’ in the name as a word delimiter?

So to sum up, I need to match ‘m’ in a string, but not ‘s/m’ or ‘small’, etc.. Any help is appreciated.

Answer 1

%\b(?<![/-])(m|med|medium)(?![/-])\b%

You can use negative lookbehind or lookahead to exclude the offending separators. This means "m"/"med"/"medium" which is its own word, but not preceded or followed by a slash or a dash. It also works on the beginning and end of string, since negative lookahead/lookbehind do not force a matching character to be present.

If you only want to delimit on whitespace, you can use the positive version:

%\b(?<=\s|^)(m|med|medium)(?=\s|$)\b%

("m"/"med"/"medium" which is preceded by whitespace or the start of the string, and followed by whitespace or the end of the string)