php - split by unknown regular expression

Question

I need to split a string by seperators that are known to me and also unknown. For example i know i want to split the string by "\n" and "," and "." but also 1 sperator that can be user defined: for example it can be ";" or "hello" or pretty much anything.

I tried this:

"[\n|,|.|".$exp."]"

...but that didnt work as expected. As i understand | means or. So this reg exp should say that split by "\n" or "," or "." or "hello". I think its because if i try just [hello] then it splits by every letter, not the whole word. Thats strange because if i try just [\n] then it only splits by "\n" - not by "\" or "n".

Can someone please explain this to me? :)

the brackets is used to define a list of character, [ab] is a or b, it is the same as a|b — SmasherHell
– SmasherHell, Commented May 18, 2013 at 23:42

Patashu · Accepted Answer · 2013-05-19 00:09:37Z

6

When you place a bunch of characters in a character class, as in [hello], this defines a token that matches one character that is either h, e, l or o. Also, | has no meaning inside of a character class - it's just matched as a normal character.

The correct solution isn't to use a character class - you meant to use normal brackets:

(\n|,|\.|".$exp.")

By the way - make sure that you escape any regex metacharacters that are in $exp. Basically, the full list here needs to be escaped with backslashes: http://regular-expressions.info/reference.html There may be a helper function to do it for you.

EDIT: Since you're not using a character class, we now need to escape \ the . which is now a metacharacter meaning 'match one of anything'. Almost forgot.

edited May 19, 2013 at 0:09

answered May 18, 2013 at 23:42

Patashu

21.8k4 gold badges49 silver badges53 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

user1985273 Over a year ago

Got it, Thank you and everyone else who anwsered :)

Zach Johnson · Accepted Answer · 2013-05-18 23:40:34Z

1

\n is actually only one character, a new line, (the \ before the n indicates an escape sequence) so that's why it works and hello doesn't.

Also, keep in mind that allowing arbitrary input into a regular expression can be a security risk, depending on what your regular expression is being used for, so be very careful and make sure you sanitize your input to that regular expression.

answered May 18, 2013 at 23:40

Zach Johnson

24.3k7 gold badges71 silver badges86 bronze badges

Comments

Vedran Šego · Accepted Answer · 2013-05-18 23:42:17Z

1

Try using this regex:

preg_split('#[\n,.]|'.$exp.'#', ...);

Note the single quots, to avoid \n getting replaced by the new line.

answered May 18, 2013 at 23:42

Vedran Šego

3,8153 gold badges31 silver badges43 bronze badges

Comments

Explosion Pills · Accepted Answer · 2013-05-18 23:42:33Z

1

Drop the [ and ] as these define a character class. \n counts as a single character in a double-quoted string. Just using the string without the character class should work as you need:

preg_split("/\n|,|.|$exp/", $input)

answered May 18, 2013 at 23:42

Explosion Pills

192k56 gold badges341 silver badges417 bronze badges

Comments

Sumoanand · Accepted Answer · 2013-05-18 23:48:44Z

1

Use preg_split()

For example:

Input:

$exp = '#';
preg_split("/[,.\n$exp]/", "0\n1,2.3#4")

Output:

Array ( [0] => 0 [1] => 1 [2] => 2 [3] => 3 [4] => 4)

edited May 18, 2013 at 23:48

answered May 18, 2013 at 23:42

Sumoanand

8,9293 gold badges50 silver badges46 bronze badges

Comments

Desolator · Accepted Answer · 2013-05-19 02:16:39Z

1

here is a simple solution:

"(\n|,|\.|".$exp.")"

or you can do it like:

"([\n,.]|".$exp.")"

edited May 19, 2013 at 2:16

answered May 18, 2013 at 23:45

Desolator

22.8k20 gold badges76 silver badges100 bronze badges

2 Comments

Patashu Over a year ago

You have it backwards, you need to escape . when it's outside of a character class and not when it is.

Desolator Over a year ago

didn't notice that.. fixed

Collectives™ on Stack Overflow

php - split by unknown regular expression

6 Answers 6

1 Comment

Comments

Comments

Comments

Comments

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

6 Answers 6

1 Comment

Comments

Comments

Comments

Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related