PHP username Regular expression (Chinese, English, digit, letter)

PHP Tutorial User name Regular expression (Chinese, English, digit, letter)
Consists of a letter a~z (case-insensitive), a numeric 0~9, a minus sign, or an underscore
You can only start and end a number or letter with a 4~18 character length

^[a-za-z0-9]{1}[a-za-z0-9|-|_]{2-16}[a-za-z0-9]{1}$

The user name is uppercase or lowercase letters or underscores and begins with a letter with a length of 6-20

^[A-ZA-Z][WD_]{5,19}

User name: including English lowercase, Chinese characters, numbers, underscores, cannot be all numbers, underline cannot be at the end

/^[a-z0-9_u4e00-u9fa5]+[^_]$/g

Utf-8 under

Preg_match ("/^[a-z0-9_x80-xff]+[^_]$/g", $a);

GBK under:

Preg_match ("/^[a-z0-9_". Chr (0XA1). " -". Chr (0xFF)."] +[^_]$/", $a)

Can have Chinese user name verification

[A-za-z0-9] [U4e00-u9fa5]

Because we write an expression that matches any part of a string. It will not only think ' mike_84′ is a legitimate string, it will also match similar '%! mike_84& ' This string that contains something we don't want to appear in. We need to use line anchors, ^ (caret) and $ (dollar) characters will limit our expression to the start and end of a string to ensure that the entire username fits our set, not part of it.

So the regular expression of the revised version looks like this:
/^[a-za-z0-9_]{3,16}$/