Regular expression that matches given pattern and ends with optional number - php

Question

I've been trying to use a regular expression to match and extract parts of a URL.
The URL pattern looks like:
http://domain.abcdef/xyz/fe/fi/fo5/fu2m/123/
I intend to capture the following groups:
match and capture xyz (optional, but specific value)
match and capture fe/fi/fo5/fu2m (must exist, arbitrary value)
match and capture 123 (optional numeric value, which must appear at the end)
Here are expressions I have tried and problem encountered:
string1: http://domain.abcdef/xyz/fe/fi/fo5/fu2m/123/
string2: http://domain.abcdef/xyz/fe/fi/fo5/fu2m/
^(?:https?:\/\/)?(?:[\da-z\.-]+)\.(?:[a-z\.]{2,6})(?:\/(xyz))?\/([\/\w]+)+(?:\/([\d]+))\/$
makes number at end mandatory
matches and captures all groups as required in string1 even when xyz is not included
no match in string2 because there's no number at the end
^(?:https?:\/\/)?(?:[\da-z\.-]+)\.(?:[a-z\.]{2,6})(?:\/(xyz))?\/([\/\w]+)+(?:\/([\d]+))?\/$
makes number at end optional
captures only groups 1 and 2 in string1 and string2 . Number is matched along with group 2 in string2 as fe/fi/fo5/fu2m/123
My problem is how to capture groups 1, 2 and 3 in all scenarios incl. string1 and string2 (note: I am using PHP's preg_match function)

Answer 1

I will use parse_url first to extract the path from the url. Then all you have to do is to use a non-greedy quantifier in the second group :
$path = parse_url($url, PHP_URL_PATH);
if ( preg_match('~^\A/([^/]+)/(.*?)/(?:(\d+)/)?\z~', $path, $m) )
var_dump($m);
This way, if the number at the end is missing, the non-greedy quantifier (from the second group) is forced to reach the end of the string.

Answer 2

Use a modified URL validator.
'~^(?!mailto:)(?:(?:https?|ftp)://)?(?:\S+(?::\S*)?#)?(?:(?:(?:[1-9]\d?|1\d\d|2[01]\d|22[0-3])(?:\.(?:1?\d{1,2}|2[0-4]\d|25[0-5])){2}(?:\.(?:[1-9]\d?|1\d\d|2[0-4]\d|25[0-4]))|(?:(?:[a-z\u00a1-\uffff0-9]+-?)*[a-z\u00a1-\uffff0-9]+)(?:\.(?:[a-z\u00a1-\uffff0-9]+-?)*[a-z\u00a1-\uffff0-9]+)*(?:\.(?:[a-z\u00a1-\uffff]{2,})))|localhost)(?::\d{2,5})?(?:/(xyz))?((?:/(?!\d+/?$)[^/]*)+)(?:/(\d+))?/?\s*$~'
Group 1 is optional xyz
Group 2 is required middle
Group 3 is optional number at the end
Readable version
^
(?! mailto: )
(?:
(?: https? | ftp )
://
)?
(?:
\S+
(?: : \S* )?
#
)?
(?:
(?:
(?:
[1-9] \d?
| 1 \d\d
| 2 [01] \d
| 22 [0-3]
)
(?:
\.
(?: 1? \d{1,2} | 2 [0-4] \d | 25 [0-5] )
){2}
(?:
\.
(?:
[1-9] \d?
| 1 \d\d
| 2 [0-4] \d
| 25 [0-4]
)
)
| (?:
(?: [a-z\u00a1-\uffff0-9]+ -? )*
[a-z\u00a1-\uffff0-9]+
)
(?:
\.
(?: [a-z\u00a1-\uffff0-9]+ -? )*
[a-z\u00a1-\uffff0-9]+
)*
(?:
\.
(?: [a-z\u00a1-\uffff]{2,} )
)
)
| localhost
)
(?: : \d{2,5} )?
(?:
/
( xyz ) # Optional specific value
)?
( # Must exist, arbitrary value
(?:
/
(?! \d+ /? $ ) # Not a numeric value at the end
[^/]*
)+
)
(?:
/
( \d+ ) # Optional numeric value, which must appear at the end
)?
/?
\s*
$
Output
** Grp 0 - ( pos 0 : len 46 )
http://domain.abcdef/xyz/fe/fi/fo5/fu2m/123/
** Grp 1 - ( pos 21 : len 3 )
xyz
** Grp 2 - ( pos 24 : len 15 )
/fe/fi/fo5/fu2m
** Grp 3 - ( pos 40 : len 3 )
123
** Grp 0 - ( pos 48 : len 42 )
http://domain.abcdef/xyz/fe/fi/fo5/fu2m/
** Grp 1 - ( pos 69 : len 3 )
xyz
** Grp 2 - ( pos 72 : len 18 )
/fe/fi/fo5/fu2m/
** Grp 3 - NULL