Check if a string only contains "A-Za-z0-9_" and "."

[stanleyhsieh]

Hi all!
I'm new here!

I was wondering how I can check if a string contains only "A-Za-z0-9_" and ".".
I tried the following code

[php]
function check_validstring($check_validstring)
{
if(eregi('[A-Za-z0-9_.]',$check_validstring))
{
return true;
}
else
{
return false;
}
[/php]

The result is:

When $check_validstring = 'aaa' it passed.
When $check_validstring = '@@' it failed.
But When $check_validstring = 'aaa@@' it passed.

Any way to prevent this? Thanks!

[MarkoKlacar]

Hi,

have you looked at this?

[stanleyhsieh]

Sure I did.
I thought they are the same thing, other than the fact that eregi is not case-sensitive.

[MarkoKlacar]

Hi,

when I look at you code, it acts correctly.
What I think you can do is add an extra if-condition explicitly looking for the characters that are not allowed.

Let me know.

Cheers

[stanleyhsieh]

Thanks for your reply.
I appriciated very very much.

I would like to know, how can I use a if to prevent this from happening?
Thanks!

[MarkoKlacar]

Hi,

well the if statement could look like this:

[PHP]
else if(eregi('[@]',$check_validstring))
return false;
[/PHP]

When you do:
[PHP]
if(eregi('A-Za-z0-9_.',$check_validstring))
[/PHP]

The only thing you say is as long as there is an A or a etc the string is ok (it returns true).

Now what you can do is look at this and read about how you can limit characters, you will find something useful trust me.

Cheers

[stanleyhsieh]

Thanks for you help!
I finally got it working.

Here's the code that should work.
[PHP]
function check_charators($string)
{
if(ereg('^[A-Za-z0-9_][A-Za-z0-9_]*$', $string))
{
return true;
}
else
{
return false;
}
}
[/PHP]

I delete the "." ;)