How to correct my regex to not match particular expressions starting with a character

Question

In PHP I am trying to create a regex without success, which should match expressions consisting of numbers and a single 'end'character, only of the numbers are not preceeded by an F. Here is an exmaple string to match

$test = "123A456C789XF765S333333AF444G";

and the following regex

preg_match_all("/(?<!F)(\d+)([ASTCGX])+/", $test, $matches)

finds the following expressions:

123A
456C
789X
65S
33333A
44G

while I expect only the following matches:

123A
456C
789X
333333A

I do not want to have the numbers \d+ split up to match the regex. An expression like F\d+[ACXSG]+ should not be matched! How to achieve this?

Answer 1

I suggest you to use this:

preg_match_all("/(?<![\dF])(\d++)([ASTCGX])/", $test, $matches);

explanation:

(?<![\dF])       # not preceded by F or a digit (numbers can't be trunked)
\d++             # one or more digit (with a possessive quantifier, optional but better)
[ASTCGX]         # one of these characters