Q:

Fatal error: Can't use function return value in write context in

I have this code for check if isset MySQL data and check for int : 
<input type="radio" name="lang"  value="1"
<?PHP if(isset(filter_var($__SQL__[0]['lang'], FILTER_VALIDATE_INT))){  
      echo ($__SQL__[0]['lang'] == 1 ? ' checked="checked"' : '');}?>
 />

But I See This Error:
Fatal error: Can't use function return value in write context in 
C:\xampp\htdocs\user\modules\editnews.php on line 56

how do can I fix this error?

A:

It's a limitation of PHP. You are using isset(), which is not a function, but a language construct. You can only use it on simple variables, in PHP versions prior to 5.5. See the documentation:

Prior to PHP 5.5, empty() only supports variables; anything else will result in a parse error. In other words, the following will not work: empty(trim($name)). Instead, use trim($name) == false.

That means that you need to do something like this:
// We'll check if $__SQL__[0]['lang'] exists and
// the filter_var succeeds.
if (isset($__SQL__[0]['lang']) && filter_var($__SQL__[0]['lang'], FILTER_VALIDATE_INT) !== false) {
    echo ($__SQL__[0]['lang'] == 1 ? ' checked="checked"' : "");
}

