regex match URL path only with specific chars?

Question

I search a regex in PHP to match a simple URL path with specific characters and not more.

My regex don't work exactly (flag 'gm' only for test. in working process please without 'g' for more exactly.):

/^\/[A-Za-z0-9-]+\/?[A-Za-z0-9-]+\/?[A-Za-z0-9-]+\/?[A-Za-z0-9-]+\/?$/gm

URL path Examples with comment:

#match: YES
/
/trip-001
/trip-001/
/trip-001/summer-2019
/trip-001/summer-2019/
/trip-001/summer-2019/ibiza-001/
/trip-001/summer-2019/ibiza-001/PICT-001

#match: NO
//
trip-001
trip-001/
trip-001/summer-2019
trip-001/summer-2019/
trip-001/summer-2019/ibiza-001/
trip-001/summer-2019/ibiza-001/PICT-001

//trip-001
trip-001//
//trip-001/summer-2019
//trip-001//summer-2019
trip-001//summer-2019
//trip-001/summer-2019/
//trip-001//summer-2019//
trip-001//summer-2019/
trip-001/summer-2019//
trip-001/summer-2019/
trip-001/summer-2019/ibiza-001/
//trip-001/summer-2019/ibiza-001/
//trip-001//summer-2019/ibiza-001/
//trip-001/summer-2019//ibiza-001/
//trip-001/summer-2019/ibiza-001//
trip-001/summer-2019/ibiza-001//
trip-001/summer-2019/ibiza-001/
trip-001/summer-2019/ibiza-001/PICT-001
//trip-001/summer-2019/ibiza-001/PICT-001
# and similar

/trip-001/summer-2019/ibiza-001/PICT-001/
/trip-001/summer-2019/ibiza-001/whatever-987/PICT001
/trip-001/summer-2019/ibiza-001/whatever-987/PICT001/

trip-001/summer-2019/ibiza-001/PICT-001/
trip-001/summer-2019/ibiza-001/whatever-987/PICT001
trip-001/summer-2019/ibiza-001/whatever-987/PICT001/

I have no idea it works with {n}.

Only this charset: A-Z a-z 0-9 - / and exactly no more. Please no \d for digits.

It's for a !preg_match() in PHP.

EDIT: Leading slash is a must have. Double slash and more is not allowed. Trailing slash yes or no.

Wiktor Stribiżew · Accepted Answer · 2020-04-19 18:40:24Z

1

It appears the URL should only be valid if there are not more than 5 slashes.

You may adjust your pattern as

^(?!(?:[^\/]*\/){5})(?:(?:\/[A-Za-z0-9-]+){1,4}\/?|\/)$

See regex demo

Details

^ - start of string
(?!(?:[^\/]*\/){5}) - a negative lookahead that fails the match if there are 5 occurrences of / chars in the string
(?: - start of the non-capturing group:
- (?:\/[A-Za-z0-9-]+){1,4}\/? - 1 to 4 occurrences of a / and 1+ ASCII alphanumeric or - chars and then an optional / char
- | - or
- \/ - a single / char in the string
) - end of the non-capturing group
$ - end of string.

edited Apr 19, 2020 at 18:40

answered Apr 19, 2020 at 17:05

Wiktor Stribiżew

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11 Comments

Wiktor Stribiżew Over a year ago

@Malama Correct. That is what I suggest, too. See updated samples demo.

Wiktor Stribiżew Over a year ago

@Malama (?:[^\/]*\/){5} matches 5 occurrences of any 0+ chars other than / followed with /. It is a pattern inside a negative lookahead, it just fails any string that has 5 or more / chars in it. You do not need to replace it with any pattern, the consuming pattern will validate the string. (?:...) is a non-capturing group.

Wiktor Stribiżew Over a year ago

@Malama Both my regexps require / as the first char. See your updated sample demo. If you need more clarifications please ask here, add more comments.

Wiktor Stribiżew Over a year ago

@Malama Is empty string allowed?

Wiktor Stribiżew Over a year ago

@Malama I fixed the pattern in the answer.

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