Searching for multiple elements with regex

Question

How can I check for a variable number of elements in a string?

[keyword1|keyword2|keyword3]
[keyword1|keyword2]

... or more than three keywords. This would just work for three elements:

preg_match("/^\[(.*)\|(.*)\|(.*)\]$/",$string, $matches)

Edit: How can I get the captured keyword in variables? i.e.:

matches[1] = keyword1
matches[2] = keyword2
matches[3] = keyword3

You'll need two separate patterns, one to validate the string, and one to extract the keywords. — Aran-Fey, Dec 26 '14 at 16:12
@AvinashRaj: Variable Number, that means 1 or more keyword in that string (beginning with [ and ending with ]) — user3142695, Dec 26 '14 at 16:13

score 2 · Answer 1 · edited May 23 '17 at 12:28

2

You can use:

(?:^\[(?=[^][|]*(?:\|[^][|]*)*\])|(?!^)\G)([^][|]*)(?:[]|])

Regular expression visualization

This technique is explained in details HERE

edited May 23 '17 at 12:28

Community

answered Dec 26 '14 at 16:16

Enissay

@user3142695 It looks scary, but once you read the doc (link above) you'll see how much it's simple :) – Enissay Dec 26 '14 at 16:27
@AvinashRaj it's true that the `(?=...)` is not needed here, it only controls how many results to grab... Removing it will give a similar pattern to yours, so I'll leave it – Enissay Dec 26 '14 at 17:05

Avinash Raj · Accepted Answer · 2014-12-26T16:35:12.313

1

Use this, 3 and more.

^\[[^|\n]*(?:\|[^|\n]*){2,}\]$

FOr more than 3,

^\[[^|\n]*(?:\|[^|\n]*){3,}]$

You could do simply like this through \G anchor,

(?:^\[|\G)\|?([^\n|\]]+)(?=[\]|])

Use \G anchor to do a continuous string match.

edited Dec 26 '14 at 16:35

answered Dec 26 '14 at 16:02

Avinash Raj

`preg_match("/^\[[^|\n]*(?:\|[^|\n]*){2,}\]$/",$string, $matches)` So my result would be: $matches[1], $matches[2], ... $matches[n]. Correct? – user3142695 Dec 26 '14 at 16:07
no, it matches that particular line only. Did you want to capture the keywords? Could you edit the question with expected output? – Avinash Raj Dec 26 '14 at 16:08
Yes, sorry for the unsufficient question. Updated the question. – user3142695 Dec 26 '14 at 16:09
In the regex101.com-link every second result is empty? `match1 = 'keyword 1', match2 = ''` and so on... – user3142695 Dec 26 '14 at 16:30
I think you could filter out the empty strings from an array easily. – Avinash Raj Dec 26 '14 at 16:32

2 Answers2