Question

How to restrict characters used for a username?

Comments

Can somebody tell me ? Only a~z _ 0~9 can be used

Answer 1

This question has some detail in the comments. In your case you'd probably want to use preg_match like this:

    preg_match('/^[a-zA-Z0-9_]+$/', $handle, $matches)

 

Comments

Where do I put this code?
qa-app-users-edit.php or qa-filter-basic.php or ... ?
sorry i'm an amateur.

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Follow the instructions in the comment on the linked question. It starts "Open qa-app-users-edit.php for edit".

Then instead of where it says:
  preg_match('/admin|moderator/', $handle, $matches)
You would put:
  preg_match('/^[a-zA-Z0-9_]+$/', $handle, $matches)

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Hi @Scott, could you please help me to implement this on the version 1.7.4. I tried to make it work by following steps. However after I made changes to the code, it doesn't allow (a~z _ 0~9) any of this characters to be used, but every other characters work except the following 3 characters @ / +.

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@Ankhamax the best way in the latest Q2A is to make a filter module: http://docs.question2answer.org/plugins/modules-filter/
You'll want to use the filter_handle method.

What characters exactly do you want to restrict in the username? If you want to limit to only alphanumeric characters then the above regex in my answer will work.