The regular expression match is incorrect? How to solve

The regular expression match is incorrect? PHPcodeif (! Preg_match ($ user_name, [^ a-zA-Z0-9 _ @.] g) {echo cannot contain Chinese characters.} the above code cannot verify that the user name is not composed of English numbers or underscores. ------ solution ---------------- The parameter order is reversed. ------ solution ------------- is the regular expression matching incorrect?

PHP code

  If (! Preg_match ($ user_name, '/[^ \ a-\ z \ A-\ Z0-9 \ _ @ \.]/g') {echo' Chinese is not allowed ';}

The above code cannot verify that the user name is not composed of English numbers or underscores

------ Solution --------------------
The parameter order is reversed.
------ Solution --------------------
If (! Preg_match ('/^ [a-z0-9 _] + $/I', $ user ))
{
Echo 'Chinese is not allowed ';
}

Try this way.