Programming

  minte9
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Variables / Exists

Downsides

There is no way to ensure that any one of variables will exist at any given point. 
 
/**
 * There are downsides of the way PHP handles variables.
 * There is no way to ensure that any one of them ...
 * will exist at any given point
 * 
 * isset() will return TRUE if a variable ...
 *      exists and has a value other than NULL
 * 
 * empty() will returns TRUE if a variable ...
 *      has a empty and zero value ("", 0, NULL)
 */

if(isset($a) && $a != "")
    echo 1;

if(!empty($a)) // better
    echo 1;

Check

Empty() checks only variables as anything else will result in a parse error. 
 
/**
 * isset() - determine if a variable is set and is not NULL
 * empty() - determine whether a variable is empty
 */

$a = 1;
$b = 0;
$c = "";
$d = null;

echo isset($a)      ? 1 : 0; // 1
echo isset($b)      ? 2 : 0; // 2
echo isset($c)      ? 3 : 0; // 3
echo isset($d)      ? 4 : 0; // 0

echo empty("")      ? 5 : 0; // 5
echo empty(0)       ? 6 : 0; // 6
echo empty("0")     ? 7 : 0; // 7
echo empty(NULL)    ? 8 : 0; // 8
echo empty(false)   ? 9 : 0; // 9
echo empty(array()) ? 1 : 0; // 1




References