php empty() checks whether a variable is empty_PHP tutorial-PHP Tutorial-php.cn

php empty() checks whether a variable is empty_PHP tutorial

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Release： 2016-07-21 15:23:14

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empty — Check if a variable is empty

Report a bug Description

bool empty ( mixed $var )
If var is a non-empty or non-zero value, Then empty() returns FALSE. In other words, "", 0, "0", NULL, FALSE, array(), var $var; and objects without any properties will be considered empty, and TRUE is returned if var is empty.

empty() is the antonym of (boolean) var, except that it does not produce a warning when the variable is not set. See Converting to Boolean for more information.

Example #1 A simple comparison between empty() and isset().

Copy code The code is as follows:

 
$var = 0; 
// Result is true because $var is empty
if (empty($var)) { 
echo '$var is either 0 or not set at all'; 
} 
// The result is false, Because $var is set
if (!isset($var)) { 
echo '$var is not set at all'; 
} 
?> 

Note: Because it is a language constructor rather than a function, it cannot be called by variadic functions.

Note:

empty() only tests variables, testing anything that is not a variable will result in a parsing error. In other words, the following statement will not work: empty(addslashes($name)).

The following things are considered to be empty:

"" (an empty string)
0 (0 as an integer)
0.0 (0 as a float)
"0" (0 as a string)
NULL
FALSE
array() (an empty array)
var $var; (a variable declared, but without a value in a class)
Understanding of "empty array": array() (an empty array)

Copy code The code is as follows:

 
$array1=array(); 
print_r($array1); 
if(empty($array1)){ 
echo 'Yes empty() is an empty array'; 
} 
else{ 
echo 'For empty() is a noempty array'; 
} 
?> 
//Display results: ##################### 
Array 
( 
) 
 //For empty() it is an empty array 
############################## 
< ;?php 
$array1=array(); 
$array1[]=''; 
print_r($array1); 
if(empty($array1)){ 
echo ' An empty array for empty()'; 
} 
else{ 
echo 'An empty array for empty()'; 
} 
?> 
//Display results: ##################### 
Array 
( 
[0] => 
) 
//It is a noempty array for empty() 
//################## ############ 
//This is not an empty array, because it has an element with an empty character (""), please pay attention to the empty character ("" (an empty string)) Difference; 