Home > Article > Backend Development > Example tests of PHP empty(), isset() and is_null()_PHP tutorial
Example tests of PHP empty(), isset() and is_null()_PHP tutorial
- WBOYOriginal
- 2016-07-14 10:07:30941browse
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($f));
?>
The program output is:
bool(true)
bool(true)
bool(true)
bool(true)
bool(true)
bool(true)
As can be seen from the code, empty() outputs true as long as the data type is empty or false.
isset()
Look at the output of isset:
var_dump(isset($a));
var_dump(isset($b));
var_dump(isset($c));
var_dump(isset($d));
var_dump(isset($e));
var_dump(isset($f));
// Output
bool(false)
bool(true)
bool(true)
bool(true)
bool(false)
bool(true)
It can be seen that isset() can only be used to determine whether it is NULL and undefined.
is_null()
Finally is the output of is_null:
var_dump(is_null($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(false)
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.
Statement：
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
Previous article：Use php to execute shell command under linux to view the server's machine name_PHP tutorialNext article：Use php to execute shell command under linux to view the server's machine name_PHP tutorial