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

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

1. empty function isset function is used to detect whether this variable has been set. In the following two cases, isset will be considered false ①$id; No value is given② Or there is no definition at all. Therefore, we recommend using isset to determine whether a form is submitted with data if(isset($_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($a1) ? ‘true’ : ‘false’;//output trueecho empty($a2) ? ‘true’ : ‘false’;//output trueecho empty($a3) ? ‘true’ : ‘false’;//output trueecho empty($a4) ? ‘true’ : ‘false’;//output trueecho empty($a5) ? ‘true’ : ‘false’;//output trueecho empty($a6) ? ‘true’ : ‘false’;//output falseecho empty($a7) ? ‘true’ : ‘false’;//output trueecho empty($a8) ? ‘true’ : ‘false’;//output falseecho ‘
’;echo isset($a1) ? ‘true’ : ‘false’;//output falseecho isset($a2) ? ‘true’ : ‘false’;//Output trueecho isset($a3) ? ‘true’ : ‘false’;//Output trueecho isset($a4) ? ‘true’ : ‘false’;//output trueecho isset($a5) ? ‘true’ : ‘false’;//output trueecho isset($a6) ? ‘true’ : ‘false’;//Output trueecho isset($a7) ? ‘true’ : ‘false’;//output trueecho isset($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.