[SOLVED] Regular Expressions

[chriskiely]

Hello, I am writing a form validation script in php and have got the whole thing working except for checking to see if the username supplied by the user is in the correct format (i.e. contains only letters, numbers and the underscore character). This the code I have come up with but it always produces the error message. I have to say I don't really understand the syntax for creating regular expressions so I am assuming this is where I am going wrong. ($user_name is passed from the form)

 

$user_name=stripslashes($user_name);

$user_name=trim($user_name);

$user_name=strtolower($user_name);

 

if(!eregi("^[A-Za-z0-9\_$", $user_name)){

    $errmsg.='Invalid user name, please try again.';

}

 

Any help would be really appreciated as this is driving me mental!!

Thanks, Chris

[taith]

your missing an ]

[chriskiely]

ah yes sorry, but still trying it like "[^A-Za-z0-9\_$]" and "^[A-Za-z0-9\_]$" doesn't work either... i am testing it with words such as "chris" "chris1" "chris_1" etc, all of them fail the test and produce the error message....

[taith]

^[A-Z][a-z][0-9][\_]$

 

^ <-- start of string

$ <-- end of string

[] <-- conditionals

[MadTechie]

 

use

^[A-Za-z0-9\_]+$

 

as "chris" "chris1" are more than one char

[chriskiely]

ah i was missing the plus... thanks very much indeed for your help!