Double regex matches - php

Question

I'm preg_match_all looping through a string using different patterns. Sometimes these patterns look a lot like each other, but differ slightly.
Right now I'm looking for a way to stop pattern A from matching strings that only pattern B - which has a 'T' in front of the 4 digits - should match.
The problem I'm running into is that pattern A also matches pattern B:
A:
(\d{4})(A|B)?(C|D)?
... matches 1234, 1234A, 1234AD, etc.
B:
I also have another pattern:
T(\d{4})\/(\d{4})
... which matches strings like: T7878/6767
The result
When running a preg_match_all on "T7878/6767 1234AD", A will give the following matches:
7878, 6767, 1234AD
Does anyone have a suggestion how to prevent A from matching B in a string like "Some text T7878/6767 1234AD and some more text"?
Your help is greatly appreciated!

Answer 1

Scenario with boundaries
If you only want to match those specific strings within some boundaries, use those boundary patterns on each side of the pattern.
If you expect a whitespace boundary before each match, then add the (?<!\S) negative lookbehind at the start of the pattern. If you expect a whitespace boundary at the end of the match, add the (?!\S) negative lookahead. If there can be any chars (as is in your original question), then SKIP-FAIL is the only way (see below).
So, in this first case, you may use
(?<!\S)(\d{4})([AB]?)([CD]?)(?!\S)
and
(?<!\S)T(\d{4})\/(\d{4})(?!\S)
See Pattern 1 demo and Pattern 2 demo.
Scenario with no specific boundaries
You need to make sure the second pattern is skipped when you parse the string with the first one. Use SKIP-FAIL technique for this:
'~T\d{4}/\d{4}(*SKIP)(*F)|(\d{4})(A|B)?(C|D)?~'
See the regex demo.
If you do not need the capturing groups, you may simplify it to
'~T\d{4}/\d{4}(*SKIP)(*F)|\d{4}[AB]?[CD]?~'
See another demo
Details
T\d{4}/\d{4} - T followed with 4 digits, / and another 4 digits
(*SKIP)(*F) - the matched text is discarded and the next match is searched from the matched text end
| - or
\d{4}[AB]?[CD]? - 4 digits, then optionally A or B and then optionally C or D.

Answer 2

From what you're asking, your current regexes don't really work. (A|B)?(C|D)? will never match AB. So I think you meant [ABCD]
Here's your new regex:
T(\d{4})\/(\d{4}) (\d{4}[ABCD]*)
For the string input:
T7878/6767 1234AB
We get the groups:
Match 1
Full match 0-17 `T7878/6767 1234AB`
Group 1. 1-5 `7878`
Group 2. 6-10 `6767`
Group 3. 11-17 `1234AB`
Regex101

Answer 3

Your syntax is pretty specific, so you regex just needs to be. Get rid of all your capture groups because they are screwing things up. You only need two groups which match your string syntax exactly.
First groups looks for word bounday followed by T then 4 digits then / then 4 more digits and a word break.
Second groups matches 4 digits and then letters A-D between 0 and 2 times. It has a negative lookbehind so will only match if there is a whitespace character before the 4 digits
(\bT\d{4}\/\d{4}\b)|(?<!\S)(\d{4}[A-D]{0,2})
Preg match all output:
Array
(
[0] => Array
(
[0] => T7878/6767
[1] => 1234AB
)
[1] => Array
(
[0] => T7878/6767
[1] =>
)
[2] => Array
(
[0] =>
[1] => 1234AB
)
)