preg_match to validate a URL slug

Question

I am letting the user create their own profile on my site so they can choose what their url will be. So for example if their name is John Smith they might like to enter john-smith and then their profile URL would be www.mysite.com/john-smith.

I need to use preg_match to validate that what they enter is a valid URL slug. So here are the rules that it must fulfill to be valid:

it must contain at least one letter and it can only contain letters, numbers and hyphens

Can someone help me out please I am good at PHP but rubbish with regex!

Elias Dorneles · Accepted Answer · 2012-12-08 02:58:39Z

I hope this code is self-explanatory:

<?php function test_username($username){ if(preg_match('/^[a-z][-a-z0-9]*$/', $username)){ echo "$username matches!\n"; } else { echo "$username does not match!\n"; } } test_username("user-n4me"); test_username("user+inv@lid")

But if not, the function test_username() test its argument against the pattern:

begins (^) ...
with one letter ([a-z]) ...
followed by any number of letters, numbers or hyphens ([-a-z0-9]*) ...
and doesn't have anything after that ($).

Arthur Ronconi · Accepted Answer · 2019-08-20 16:13:29Z

7

Better solution:

function is_slug($str) { return preg_match('/^[a-z0-9]+(-?[a-z0-9]+)*$/i', $str); }

Tests:

fail: -user-name
fail: user--name
fail: username-
valid: user-name
valid: user123-name-321
valid: username
valid: USER123-name
valid: user-name-2

Enjoy!

edited Aug 20, 2019 at 16:13

answered Aug 7, 2016 at 0:15

Arthur Ronconi

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6 Comments

Arthur Shlain Over a year ago

something wrong, not match with user-name, only u-name regex101.com/r/0hYjoV/1

Arthur Ronconi Over a year ago

@ArthurShlain thanks. It's fixed, try again please.

Arthur Shlain Over a year ago

Now better, but check this variant: user-name-2

Arthur Ronconi Over a year ago

@ArthurShlain fixed again =)

Vicky Dev Over a year ago

How to allow underscore also with this ? Same rule need to apply as with dash, cannot occur in start/end, but can in the middle.

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lonesomeday · Accepted Answer · 2012-01-12 20:36:11Z

1

Pretty simply, if we assume that the first character must be a letter...

/[a-z]{1}[a-z0-9\-]*/i

answered Jan 12, 2012 at 20:36

lonesomeday

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