How to find this regex using PHP

Question

find all the <1></1> and <2></2> and <3></3>... in a string.

Answer 1

You can use the following regex: <[0-9]></[0-9]>

EDIT: To avoid that the search matches <2></3> too, you can use a sub-expression and a backreference to instantiate it: <([0-9])></\1>

Answer 2

<(\d+)></\1>

should work. This ensures that the regex won't match <1></4> for example.

\1 is here a backreference which must match exactly the same string as the first capturing group (the (\d+) in the first angle brackets).

Answer 3

One regex to match any of them?

<([1-3])></\1>

Should there code allow for anything to be posted in between the > and the <? Something like this then:

<([1-3])>(.*?)</\1>

Answer 4

<STYLE[^>]*>([\s\S]*?)<\/STYLE[^>]*>

Just replace STYLE with your tag like 1, 2 whatever.