编写正则表达式以获取两个分隔符之间的数字

Question

I need to parse a string and get the numbers between 2 delimiters. I need to be sure they're numbers. I tried something like this but doesn't work as expected.

if (preg_match_all("/[^0-9](?<=First)(.*?)(?=Second)/s", $haystack, $result))
for ($i = 1; count($result) > $i; $i++) {
    print_r($result[$i]);
}

What's wrong with the regex?

Answer 1

Huh, that's almost the one I supplied to your other question xD

Change the (.*?) to ([0-9]+)

if (preg_match_all("/(?<=First)([0-9]+)(?=Second)/s", $haystack, $result))
for ($i = 1; count($result) > $i; $i++) {
    print_r($result[$i]);
}

.*? will match any character (except newlines) and to match only numbers in between your delimiters "First" and "Second", you will need to change it to [0-9] . Then, I assume that there can't be nothing in between them, so we use a + instead of a * .

I'm not sure why you used [^0-9] in the beginning. Usually [^0-9] means one character which is not a number, and putting it there doesn't really do something useful, at least in my opinion.

---

Cleaning up a little, you could remove a few things that aren't needed to get the required output:

if (preg_match_all("/(?<=First)[0-9]+(?=Second)/", $haystack, $result))
   print_r($result[0]);

Answer 2

You can use [0-9] or \\d to ensure that the characters between the delimiters are numbers. using this you also won't need the lazy quantifier (unless your delimiters are actually numbers, too):

preg_match_all("/[^0-9](?<=First)(\d*)(?=Second)/s", $haystack, $result)

Or

preg_match_all("/[^0-9](?<=First)([0-9]*)(?=Second)/s", $haystack, $result)