Check for spaces in string

I have a form where a user can enter their first and last name.

I want to allow spaces, but if a user just enters spaces and nothing else, then it should be considered invalid.

For example:

Valid first name = Ann Marie

Invalid first name = space space

I tried the empty() function but it still doesn't work.

Thanks!

I want to allow spaces, but if a user just enters spaces and nothing else, then it should be considered invalid.

$var=trim($var);
if(empty($var)){
//invalid
}