PHP empty Isset is_null

Always forget the difference between these variables, refer to the next http://www.jb51.net/article/38020.htm, record the

Set several variables

<?  $a  $b false $c = "$d =  0 $e NULL  $farray?>

The first is the empty var_dump output :

<?PHPVar_dump(Empty($a)); Var_dump(Empty($b)); Var_dump(Empty($c)); Var_dump(Empty($d)); Var_dump(Empty($e)); Var_dump(Empty($f)); ?>

The program output is:
BOOL (TRUE)
BOOL (TRUE)
BOOL (TRUE)
BOOL (TRUE)
BOOL (TRUE)
BOOL (TRUE)

Then the var_dump output of the isset:

 var_dump  (isset  ( $a   var_dump  (isset  ( $b   var_dump  (isset  ( $c   var_dump  (isset  ( $d   var_dump  (isset  ( $e   var_dump  (isset  ( $f )); 

The output is:

Output
BOOL (FALSE)
BOOL (TRUE)
BOOL (TRUE)
BOOL (TRUE)
BOOL (FALSE)
BOOL (TRUE)

And finally the var_dump output of the is_null.

 var_dump  (is_null  ( $a   var_dump  (is_null  ( $b   var_dump  (is_null  ( $c   var_dump  (is_null  ( $d   var_dump  (is_null  ( $e   var_dump  (is_null  ( $f )); 

The result of the output is:

BOOL (TRUE)
BOOL (FALSE)
BOOL (FALSE)
BOOL (FALSE)
BOOL (TRUE)
BOOL (FALSE)

This shows that empty () can be used to determine whether all data types are empty or false , and Is_null is basically the same as isset, and can only be used to determine if null and undefined .

PHP empty Isset is_null