Example tests of PHP empty(), isset() and is_null()

Example tests of PHP empty(), isset() and is_null()_PHP tutorial

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Release： 2016-07-14 10:07:30

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There has been a lot of discussion about the usage of PHP's empty(), isset() and is_null() functions, and a lot of information may not be very clear. I repeat it here again, but instead of speaking from concepts, it should be more profound to memorize it by directly using program examples.

The types of tests are as follows:

$a;

$b = false;

$c = '';

$d = 0;

$e = null;

$f = array();

empty()

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));

The program output is:

bool(true)

As can be seen from the code, empty() outputs true as long as the data type is empty or false.

isset()

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(false)

bool(true)

It can be seen that isset() can only be used to determine whether it is NULL and undefined.

is_null()

Finally is the output of 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));

// Output

bool(true)

bool(false)

bool(true)

bool(false)

is_null is literal.

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

Related labels：

empty isset null php and Example test of

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