isset problem

Why is it that I got this message:

Quote:

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

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PHP Code:

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


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Quote:

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Originally Posted by PHP.net

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

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'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'.

also you should take a look at this

Quote:

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Originally Posted by Justa Lol

also you should take a look at this

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So I should use this instead:
mysql_real_escape_string()

and the Empty function?

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

why you use mysql_real_escape_string()?

Quote:

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Originally Posted by Yearupie

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

why you use mysql_real_escape_string()?

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What should be used to avoid being hacked?

Quote:

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Originally Posted by Yearupie

why you use mysql_real_escape_string()?

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You might want to read the php manuals explanation.

Quote:

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Originally Posted by gilgalbiblewhee

What should be used to avoid being hacked?

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

Code:

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

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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().