isset problem

[gilgalbiblewhee]

Why is it that I got this message:

Fatal error: Can't use function return value in write context in \create_wlc.php on line 49

if(!isset(mysql_escape_string($_GET["book"]))){ 

[TheBigB]

isset() only works with variables as passing anything else will result in a parse error.

'mysql_escape_string' is a function and return values are apparently not accepted by 'isset'.
You may want to use the 'emtpy' function instead of 'isset', or drop the 'mysql_escape_string'.

[Justa Lol]

also you should take a look at this

[gilgalbiblewhee]

also you should take a look at this

So I should use this instead:
mysql_real_escape_string()

and the Empty function?

[Yearupie]

I should use this?
if(!isset($_GET["book"])){

why you use mysql_real_escape_string()?

[gilgalbiblewhee]

I should use this?
if(!isset($_GET["book"])){

why you use mysql_real_escape_string()?

What should be used to avoid being hacked?

[Nightwalker83]

why you use mysql_real_escape_string()?

You might want to read the php manuals explanation.

[TheBigB]

What should be used to avoid being hacked?

Well, the way you are trying it now doesn't prevent anything.
Assuming you will eventually need the value of $_GET['book'], try this:

$currentBook = mysql_real_escape_string($_GET['book']);
if(!empty($currentBook)){
    // we got 'valid' input
}

Sure you could use your original method with empty instead of isset, but you would eventually need to use mysql_real_escape_string() again when you want the value of 'book'.

Also if 'book' is an integer, you could use an (int) cast instead of mysql_real_escape_string().