PHP preg_replace - replace only strings that have max length n

Question

So I have this text:

Presedintele executiv al Miscarii Populare, Eugen Tomac, sustine ca sediul partidului din strada Pajurei, Sector 1, a fost vandalizat si ca in spatele acestei actiuni s-ar afla &, scrie Mediafax. &, a scris Eugen Tomac pe Facebook.Tomac a mai sustinut, intr-o declaratie de presa, ca locuitorii din strada Pajura ar fi primit mesaje, in numele PMP. &, a mai spus presedintele executiv.&, a mai sustinut Tomac, precizand ca a depus deja sesizare la politie.

which contains the & character inside. Every sentence ends with a . .

I have this regex: [^\.]*\&[^\.]*\.? that matches any sentence that contains the & character inside of them and then removes them, but I don't want to remove that sentence if its longer than say n characters, how do I exactly specify that in the regex?

Sebastian Proske · Accepted Answer · 2016-03-19 19:30:47Z

1

If we'd say n would be 40, you could build a regex like (?<=\.|^)(?![^\.]{40,})[^\.&]*\&[^\.]*\.?. This will only match sentences with 40 or less characters.

It uses a negative lookahead at the start of your match to ensure this and also a lookbehind to make sure, that we don't just match partial sentences. I have also added the & to the first negatet character class you are using, as it will speed up your regex a fair bit. Not sure about the ? behind \. - you might want to remove it.

I want to note, that the dot isn't necessarily the end of a sentence, but might be part of an abbreviation.

edited Mar 19, 2016 at 19:30

answered Mar 19, 2016 at 19:18

Sebastian Proske

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4 Comments

southpaw93 Over a year ago

indeed that works, but it also replaces part of the sentence that has more than 36 characters and contains & and I don't want to modify that type of sentence. Here is regex: regex101.com/r/mS6jI1/1

Sebastian Proske Over a year ago

@southpaw93 You are correct, sorry - adjusted it so it won't match partial sentences

southpaw93 Over a year ago

amazing, it works thanks for saving me hours and hours of trials :D, just one quick question, what effect does \.|^ have in that lookbehind?

Sebastian Proske Over a year ago

It ensures that the last char before the match is either the dot or the start of the string

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