Sample tests for PHPempty (), isset (), and is_null ()

PHPempty (), isset () and is_null () instance tests have been discussed a lot about the usage of PHP empty (), isset (), and is_null () functions, and a lot of information may not be clear. I will repeat it again here, but I should remember it more deeply, instead of simply using program examples to speak. The test type is as follows: PHP empty (), isset () and is_null () instance test

The usage of PHP empty (), isset (), and is_null () functions has been discussed a lot, and many materials may not be clear. I will repeat it again here, but I should remember it more deeply, instead of simply using program examples to speak.

The test type is as follows:

$a;

$b = false;

$c = '';

$d = 0;

$e = null;

$f = array();

?>

Empty ()

The first is the var_dump output of empty:

var_dump(empty($a));

var_dump(empty($b));

var_dump(empty($c));

var_dump(empty($d));

var_dump(empty($e));

var_dump(empty($f));

?>

Program output:

bool(true)

bool(true)

bool(true)

bool(true)

bool(true)

bool(true)

The code shows that empty () outputs true if the data type is null or false.

Isset ()

Let's take a look at the output of 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));

// Output

bool(false)

bool(true)

bool(true)

bool(true)

bool(false)

bool(true)

We can see that isset () can only be used to determine whether it is NULL or not.

Is_null ()

Finally, the output of is_null is as follows:

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));

// Output

bool(true)

bool(false)

bool(false)

bool(false)

bool(true)

bool(false)

Is_null.

It can be seen that empty () can be used to determine whether all data types are NULL or false, while is_null is basically the same as isset and can only be used to determine whether it is NULL or undefined.