The username must start with an alphabetical character and must NOT contain any other characters than alphanumerics, the underline and dash.
Returns TRUE on success, PEAR_Error on failure.
Table 37-1. Possible PEAR_Error values
| Error Code | Summary |
|---|---|
| FILE_PASSWD_E_EXISTS_ALREADY | the user to add already exists |
| FILE_PASSWD_E_INVALID_CHARS | the username to add contains illegal characters |