PHP: a short cut for isset and !empty?

Question

I wonder if there any better ideas to solve the problem below,

I have a form with a number of input fields, such as,

Answer 1

This function check if variable is set, is not empty, eventually if has any value.

/**
 * @param  var - testing variable
 * @param  value
 * @return boolean
 */
function is(&$var, $value = null){
  if(!is_null($value)){ return IsSet($var) && $var == $value; }
  return IsSet($var) && !empty($var);
}

echo $_GET['id'];             // this produce Warning
echo is($_GET['id'])?'1':'0'; // return false
echo $_GET['id'];             // after first using function is(), will not be produce Warning!!!

is($_GET['id']);              // return false
IsSet($_GET['id']);           // return false
$_GET['id'] = 7;
is($_GET['id'], 7);           // return true;