PHP preg_match匹配错误的字符串

Question

I have a regular expression:

/\/(register)(?:\/activate\/(.{16}))?(?:\/(student|teacher|org))?\/?$/

Correct Matching Strings:

/register
/register/student
/register/activate/1234567890123456/

Mismatch Problem:

/register/register/register/register/student/

The above still matches while using preg_match in PHP. Any alternatives?

I have also tried limiting 'register' to 1:

\/((?:register){1})(?:\/activate\/(.{16}))?(?:\/(student|teacher|org))?\/?$

No luck.

It does not match using Debuggex, however it matched using http://www.phpliveregex.com/

Debuggex Demo

Answer 1

Use a ^ at the beginning of your string to anchor it.

/^\/(register)(?:\/activate\/(.{16}))?(?:\/(student|teacher|org))?\/?$/
 * here

Without using anchor at beginning it is actually matching like below:

/register/register/register/register/student/
                           ^----------------^

Answer 2

The problem is you're only trying to match the end of the string by using $ . This means the regex will match your expression, regardless of what comes before it.

Having an expression /bob$/ will match everything that ends with bob, eg big bob . That's exactly what's happening here.

You'll need to force preg_match to match the entire string (ie both the beginning and the end) by prefixing it with ^ .

/^\/(register)(?:\/activate\/(.{16}))?(?:\/(student|teacher|org))?\/?$/