The difference between empty () and isset () in PHP
1, empty function use: detect whether the variable is null judgment: If VAR is a non-null or nonzero value, empty () returns FALSE. In other words, "", 0, "0", NULL, FALSE, Array (), Var $var; and objects that do not have any properties will be considered empty and return TRUE if Var is empty. SOURCE Manual: http://php.net/manual/zh/function.empty.php Note: empty () detects only variables and detects anything that is non-variable will result in parsing errors. $name =0; $name = "; $name =null; $name =" 0 "; $name; if (empty ($name)) {echo" OK ";//The above five notation empty ($name) are true}if (empty ($na) )//result is true because the variable $na is undefined 2, the Isset function is used: the detection variable is set to determine whether the variable is set, and is not NULL. If a variable has been freed with unset (), it will no longer be isset (). If you use Isset () to test a variable that is set to NULL, FALSE is returned. Also note that a null byte ("s") is not equivalent to a null constant in PHP. The Isset function is used to detect whether this variable has been set, and in the following two cases it is assumed that Isset is a false ① $id; There is no value ② or there is no definition at all. So we recommend determining if a form is committed with data, using Isset to determine if (isset ($_get/$_post[' variable ')} {echo $_get[' variable ']}else{echo ' No data passed '} example: $a 1 = null, $a 2 = false; $a 3 = 0; $a 4 = "; $a 5 = ' 0 '; $a 6 = ' null '; $a 7 = array (); $a 8 = array (); Echo Empty ($a 1)? ' True ': ' false ';//output Trueecho empty ($a 2)? ' True ': ' false ';//output Trueecho empty ($a 3)? ' True ': ' false ';//output Trueecho empty ($a 4)? ' True ': ' false ';//output Trueecho empty ($a 5)? ' True ': ' false ';//LoseOut Trueecho empty ($a 6)? ' True ': ' false ';//output Falseecho empty ($a 7)? ' True ': ' false ';//output Trueecho empty ($a 8)? ' True ': ' false ';//Output Falseecho '
'; Echo isset ($a 1)? ' True ': ' false ';//output Falseecho isset ($a 2)? ' True ': ' false ';//output Trueecho Isset ($a 3)? ' True ': ' false ';//output Trueecho Isset ($a 4)? ' True ': ' false ';//output Trueecho Isset ($a 5)? ' True ': ' false ';//output Trueecho Isset ($a 6)? ' True ': ' false ';//output Trueecho Isset ($a 7)? ' True ': ' false ';//output Trueecho isset ($a 8)? ' True ': ' false ';//Output True 1, isset value for the variable is not assigned or NULL when the judgment is false, the rest are true;2, empty need to pay more attention to the point, according to the definition of the function to make judgments.
http://www.bkjia.com/PHPjc/1060168.html www.bkjia.com true http://www.bkjia.com/PHPjc/1060168.html techarticle the difference between empty () and isset () in PHP 1, empty function Purpose: Detect whether the variable is null judgment: If VAR is a non-null or nonzero value, empty () returns FALSE. In other words, 0, 0 、...
