How do I test for a variable?

Anon

I have a HTML form that passes several variables to a php page.

The check boxes on the form work when checked, but if they are left unchecked, it appears as if the variable does not get passed, cuz the php chokes with a

Warning: Undefined variable: myvarname in : line of code.

Is there a way to test for the existance of a variable?

Anon

never mind.

I just
<input type="hidden" name="usingdhcp" value="0">

before my check box.

If you don't check the box, it uses the above var. If you check it, it overwrites the value with a 1. Seems to work.

jacinthe

from the manual www.php.net

isset -- Determine whether a variable is set
Description

boolean isset (mixed var)

Returns TRUE if var exists; FALSE otherwise.

If a variable has been unset with unset(), it will no longer be isset(). isset() will return FALSE if testing a variable that has been set to NULL. Also note that a NULL byte ("\0") is not equivalent to the PHP NULL constant.

empty -- Determine whether a variable is set
Description

boolean empty (mixed var)

Note: empty() is a language construct.

This is the opposite of (boolean) var, except that no warning is generated when the variable is not set. See converting to boolean for more information.