Any RegEx Experts ?

[TrumpX]

I need a regex that will match if a string does not start with 4 letters

The passed string can have 1 to n characters
however it must have 4 letters at the begining

So:
abcdefg -> no match
abcd -> no match
1bcd -> match
a-cd -> match
123 -> match
!$%? -> match
abc -> match (because at least 4 letters required)

Hope thats clear enough
This has to be done with regex only

I tried stuff like:

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/^[^a-z]{1,4}/

won't work...

[callumacrae]

Try this:

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/^[a-zA-Z]{4,}/

It returns the exact opposite of what you want, so use it like this:

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if (!preg_match('/^[a-zA-Z]{4,}/', $string))
{
	//blablabla

[AGC]

Try this:

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if (!preg_match('/^[a-zA-Z]{4,}/', $string))
{
	//blablabla

Nice. I'll add something.

To find three letters add this to the if statement.
preg_match('/[a-Z]{1,3}/', $string)

[callumacrae]

Try this:

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if (!preg_match('/^[a-zA-Z]{4,}/', $string))
{
	//blablabla

Nice. I'll add something.

To find three letters add this to the if statement.
preg_match('/[a-Z]{1,3}/', $string)

He said that it has to be four letters, and yours searches for 1 to 3 letters :/

[TrumpX]

I don't have the possibility to negate the matching result
The match has to occur within the expression itself.

I solved the problem like this

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/^(.{0,4}$|.{0,3}[^a-z])/

[AGC]

He said that it has to be four letters, and yours searches for 1 to 3 letters :/

abc -> match (because at least 4 letters required)

He gave examples.

I don't have the possibility to negate the matching result

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/^(.{0,4}$|.{0,3}[^a-z])/

You right if you want to store the matches.
Then you get wrong results.

[T0ny]

I solved the problem like this

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/^(.{0,4}$|.{0,3}[^a-z])/

Should that not be

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/^(.{0,3}$|.{0,3}[^a-z])/

otherwise it would match on abcd

[TrumpX]

I solved the problem like this

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/^(.{0,4}$|.{0,3}[^a-z])/

Should that not be

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/^(.{0,3}$|.{0,3}[^a-z])/

otherwise it would match on abcd

You are right. Thanks

[1234homie]

You dont need to use regex for that. preg_* functions is slow.. try strlen

[Erik Frèrejean]

How did you plan to use strlen for this?

Also keep in mind:

This has to be done with regex only

[callumacrae]

You dont need to use regex for that. preg_* functions is slow.. try strlen

I think you mean strstr or strpos

No, it could not be done with either of them, for several reasons:

• It has to be a regex, as the criteria specifies that it must not start with 4 letters. If you used strstr for this, you could have to execute it 456 976 times (26^4) minimum. That wouldn't be too efficient
• By "I don't have the possibility to negate the matching result", I'm guessing that means that he can only edit the regex itself, and not the code.

~Callum