Why preg_match(“/[^(22|75)]/”, “25”) returns false?

Question

I want to test that a given string does not belong to the following group of strings: 22 75.

Could anyone please tell why PHP\'s preg_match(\"/[^(22|75)]/\

Answer 1

Time for a Regular Expressions Lesson!

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Explanation of your regular expressions

[^(22|75)]

Matches false because it is looking for the following:

• A single character NOT in this list of characters: |()275

[^(22|76)]

Matches true because it is looking for:

• A single character NOT in this list of characters: |()276

Why does it do this?

You wrapped your regex in a character class (click for more info)

To give an example of how character classes work, look at this regex:

[2222222222222221111111199999999999]

This character class will only match ONE character, if it is a 2,1 or a 9.

How to make it work for you:

To match the number 25 (or 22, 52, and 55), you can use this character class:

[25]{2}

This will match a 2 digit number containing either 2 or 5 at either place.