CODEWITHSUNDEEP
phpregex
jurchiks
jurchiks

Reputation: 1433

php regex finding exact number ranges

Is there any way to check for a number in a string within an exact range using purely regex?
What I mean is that I want to check if a string contains a number that ranges, for example, from 1 to 31 in VALUE, not length.

Upvotes: 2

Views: 2021

Answers (3)

JB-Franco
JB-Franco

Reputation: 256

I use the following, hope it can helps! ;)

/^([1-2]\d|3[01]|[1-9]){1}$/

or also without the "exactly 1", be sure, the round parentheses must be present:

/^([1-2]\d|3[01]|[1-9])$/

Upvotes: 0

Álvaro González
Álvaro González

Reputation: 146450

It's obviously possible since you can always do this:

/^(1)|(2)|.....|(30)|(31)$/

And I bet the expression can be simplified for exact cases, However, IMHO it's just a way to make code unnecessarily complex to maintain.

I bet you'll enjoy this article: How do I write a regular expression that matches an IPv4 dotted address?

Upvotes: 0

Gumbo
Gumbo

Reputation: 655239

The numbers of the range from 1 to 31 can be split into two groups: one digit numbers (1–9) and two digit numbers (10–31). And the latter can further be split into whole decades (10–29) and partial decades (30–31). These can be expressed as follows:

[1-9]|[12][0-9]|3[01]

And to match only whole numbers and not just parts of them, you could use look-around assertions:

(?<!\d)([1-9]|[12][0-9]|3[01])(?!\d)

Here (?<!…) means not preceded by … and (?!…) not followed by ….

Upvotes: 3

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