Home >Backend Development >PHP Problem >How to use empty() in PHP to check whether a variable is empty
In the daily use of PHP, we often need to determine whether a variable is empty. PHP provides us with a built-in function empty() to help us check whether a variable is empty. First, let’s take a look at the syntax format:
Syntax:
empty ( mixed $var )
$var: Variables that need to be judged
Return value: When a variable does not exist, or its value is equal to false
, return true
, otherwise return false
.
PS: Before PHP 5.5, empty()
only supported variables, and checking non-numeric string offsets would return true
, PHP5.5 supports expressions.
Actual use:
1. Determine a variable that does not exist:
<?php var_dump(empty($a)); ?>
输出:bool(true)
2. Determine a variable Unassigned variable:
<?php $a; var_dump(empty($a)); ?>
输出:bool(true)
3. Judge the value of the variable to be equal to false:
<?php $a="";//0、"0"、NULL、FALSE、 array() var_dump(empty($a)); ?>
输出:bool(true)
4. Use empty() on the string offset
<?php $expected_array_got_string = 'somestring'; var_dump(empty($expected_array_got_string['some_key'])); var_dump(empty($expected_array_got_string[0])); var_dump(empty($expected_array_got_string['0'])); var_dump(empty($expected_array_got_string[0.5])); var_dump(empty($expected_array_got_string['0.5'])); var_dump(empty($expected_array_got_string['0 Mostel'])); ?>
输出: bool(true) bool(false) bool(false) bool(false) bool(true) bool(true)
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