如何编写此PHP正则表达式？

Question

I have a string of numbers surrounded by parenthesis:

(2)(56)(9)(12)(2)

I was given the following regex by someone to split the numbers out of their parentheses:

<?php

$string = '(2)(56)(9)(12)(2)';

$pattern = "/\\)\\(|\\(|\\)?/";

$numbers = preg_split($pattern, $string);

foreach ($numbers as $number) {
    echo $number.'<br />';
}

?>

This outputs:

<br />
<br />
2<br />
<br />
5<br />
6<br />
<br />
9<br />
<br />
1<br />
2<br />
<br />
2<br />
<br />
<br />

When I really need it to output:

2<br />
56<br />
9<br />
12<br />
2<br />

How can the regex be altered to make it work?

ps each number in between the parenthesis can be of an unlimited length.

Answer 1

I would not use preg_split in the first place. If that's really your source string, then look just for numbers:

preg_match_all("/\d+/", $string, $numbers);
print_r($numbers[0]);

Answer 2

First, there's an error in the regex. It should be:

$pattern = "/\\)\\(|\\(|\\)/";

Note the last ? is removed.

The easy answer is to just check for empty numbers:

foreach ($numbers as $number) {
    if ($number !== '') {
        echo $number.'<br />';
    }
}

Note the strict !== test since 0 may be a valid number...

Or, add the PREG_SPLIT_NO_EMPTY option to the preg_split call:

$numbers = preg_split($pattern, $string, -1, PREG_SPLIT_NO_EMPTY);

Another option is to use preg_match_all with the simple regex: /\\d+/ :

$matches = array();
preg_match_all('/\d+/', $string, $matches);

$numbers = $matches[0];

Answer 3

Use preg_match instead of split and use /\\\\d+/ as your expression

Try

$string = '(2)(56)(9)(12)(2)';

$pattern = "/\d+/";

preg_match_all($pattern, $string, $numbers);

foreach ($numbers as $number) {
    echo $number.'<br />';
}

I'm not sure on PHP regex syntax either \\\\d or \\d

Answer 4

You just need the PREG_SPLIT_NO_EMPTY option of preg_split, and a small change in the pattern:

$pattern = "/\\)\\(|\\(|\\)/"; // removed the "?"
$numbers = preg_split($pattern, $string, -1, PREG_SPLIT_NO_EMPTY); // added PREG_SPLIT_NO_EMPTY

Or use preg_match:

$string = '(2)(56)(9)(12)(2)';

preg_match_all('#\d+#', $string, $matches);

foreach ($matches[0] as $number) {
    echo "$number<br />\n";
}

Output:

2<br />
56<br />
9<br />
12<br />
2<br />

Answer 5

Pass the flag PREG_SPLIT_NO_EMPTY to not return empty tokens and remove the ? which allows for an empty separator. You also don't need to double-escape the () 's in PHP. Using preg_match on (\\d+) looks like it would be a simpler solution to your problem though.

$string = '(2)(56)(9)(12)(2)';
$pattern = "/\)\(|\(|\)/";
$numbers = preg_split($pattern, $string, -1, PREG_SPLIT_NO_EMPTY);
foreach ($numbers as $number) {
    echo "$number<br />\n";
}

Output:

2<br />
56<br />
9<br />
12<br />
2<br />

http://ideone.com/zxvYi