Split string into array by regular expression

Question

I need to create an array by searching a string for occurrences of '[' followed by 0 or more characters followed by ']'.

My test string:

$string="[item 1] [2] [] [item3]";

All of the above must be matched.

I think the regex to do so is

\[*\]

But how do I create an array out of the string? Do I use

preg_match_all("\[*\]", $string, $matches);

?

Answer 1

Close:

preg_match_all("!\[.*?\]!", $string, $matches);

and then $matches[0] will contain the strings.

Three changes were made:

1. Wrapped expression in ! (you can use / or whatever);
2. It's .* not * (in your example [* is saying "0 or more ["); and
3. It was made non-greedy with .*?. If you don't then you will get only one match containing basically the whole string. Take a look at Finer points of PHP regular expressions.

Answer 2

preg_match_all('/\[.*?\]/', $string, $matches);

or

preg_match_all('/\[[^\[\]]*\]/', $string, $matches);

The first one stops matching as soon as it sees a closing bracket, but it will match an opening bracket if it sees one first. That is, it would match "[ [foo]" if it's present in the input.

The second one is more robust because will only find properly balanced square brackets; ie, they can't contain square brackets. If brackets can be nested, neither regex will work; that's a much more complicated problem.

Answer 3

Try preg_split()