The difference between empty() and isset() in PHP_PHP Tutorial

The difference between empty() and isset() in PHP

1. empty function

Purpose: Check whether the variable is empty

Judgment: If var is a non-empty or non-zero value, 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. Source manual: http://php.net/manual/zh/function.empty.php

Note: empty() only detects variables, detecting anything that is not a variable will result in a parsing error.

$name=0;

$name='';

$name=null;

$name="0";

$name;

if(empty($name))

{

echo "ok"; //The above five ways of writing empty($name) are all true

}

if(empty($na)) //The result is true because the variable $na is undefined

2. isset function

Purpose: Check whether the variable is set

Judgment: Check whether the variable is set and not NULL. If a variable has been freed using unset(), it will no longer be isset(). If you use isset() to test a variable that is set to NULL, it will return FALSE. Also note that a NULL byte ("

isset function is used to detect whether this variable has been set. In the following two cases, isset will be considered false

①$id; No value is given

② Or there is no definition at all.

Therefore, we recommend using isset to determine whether a form is submitted with data if(isset($_GET/$_POST['Variable']){echo $_GET['Variable']}else{ echo 'No Pass data'}

Example:

$a1 = null;

$a2 = false;

$a3 = 0;

$a4 = '';

$a5 = '0';

$a6 = 'null';

$a7 = array();

$a8 = array(array());

echo empty($a1) ? ‘true’ : ‘false’;//output true

echo empty($a2) ? ‘true’ : ‘false’;//output true

echo empty($a3) ? ‘true’ : ‘false’;//output true

echo empty($a4) ? ‘true’ : ‘false’;//output true

echo empty($a5) ? ‘true’ : ‘false’;//output true

echo empty($a6) ? ‘true’ : ‘false’;//output false

echo empty($a7) ? ‘true’ : ‘false’;//output true

echo empty($a8) ? ‘true’ : ‘false’;//output false

echo ‘
’;

echo isset($a1) ? ‘true’ : ‘false’;//output false

echo isset($a2) ? ‘true’ : ‘false’;//Output true

echo isset($a3) ? ‘true’ : ‘false’;//Output true

echo isset($a4) ? ‘true’ : ‘false’;//output true

echo isset($a5) ? ‘true’ : ‘false’;//output true

echo isset($a6) ? ‘true’ : ‘false’;//Output true

echo isset($a7) ? ‘true’ : ‘false’;//output true

echo isset($a8) ? ‘true’ : ‘false’;//output true

1. The isset value is judged as false when the variable is not assigned a value or is assigned a value of NULL, and the rest are true;

2. There are a lot of things to pay attention to in empty, and you have to make a judgment based on the definition of the function.

http://www.bkjia.com/PHPjc/1060168.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/1060168.htmlTechArticleThe difference between empty() and isset() in PHP 1. Purpose of empty function: Detect whether the variable is empty and judge whether it is empty: If var is a non-empty or non-zero value, empty() returns FALSE. In other words, 0, 0,...