Why check both isset() and !empty()

Question

Is there a difference between isset and !empty. If I do this double boolean check, is it correct this way or redundant? and is there a shorter way

Answer 1

isset($vars[1]) AND !empty($vars[1]) is equivalent to !empty($vars[1]).

I prepared simple code to show it empirically.

Last row is undefined variable.

+-----------+---------+---------+----------+---------------------+
| Var value | empty() | isset() | !empty() | isset() && !empty() |
+-----------+---------+---------+----------+---------------------+
| ''        | true    | true    | false    | false               |
| ' '       | false   | true    | true     | true                |
| false     | true    | true    | false    | false               |
| true      | false   | true    | true     | true                |
| array ()  | true    | true    | false    | false               |
| NULL      | true    | false   | false    | false               |
| '0'       | true    | true    | false    | false               |
| 0         | true    | true    | false    | false               |
| 0.0       | true    | true    | false    | false               |
| undefined | true    | false   | false    | false               |
+-----------+---------+---------+----------+---------------------+

And code

$var1 = "";
$var2 = " ";
$var3 = FALSE;
$var4 = TRUE;
$var5 = array();
$var6 = null;
$var7 = "0";
$var8 = 0;
$var9 = 0.0;

function compare($var)
{
    print(var_export($var, true) . "|" .
        var_export(empty($var), true) . "|" .
        var_export(isset($var), true) . "|" .
        var_export(!empty($var), true) . "|" .
        var_export(isset($var) && !empty($var), true) . "\n");
}

for ($i = 1; $i <= 9; $i++) {
    $var = 'var' . $i;
    compare($$var);
}

@print(var_export($var10, true) . "|" .
    var_export(empty($var10), true) . "|" .
    var_export(isset($var10), true) . "|" .
    var_export(!empty($var10), true) . "|" .
    var_export(isset($var10) && !empty($var10), true) . "\n");

Undefined variable must be evaluated outside function, because function itself create temporary variable in the scope itself.