在PHP中解释说明[关闭]

Question

I am learning PHP. Can anyone please explain me the usage of Isset function in PHP with example. I have checked a few tutorials on internet but unable to understand them. Thanks

Answer 1

isset() only returns boolean value i.e TRUE or FALSE. Most oftent used to check if the variable is assinged or not

Let we check like this

Case 1 :

 $a = '';
 var_dump (isset($a)); // Will return TRUE

Case 2 :

$b = NULL;
var_dump (isset($a)); // Will return FALSE

Case 3 :

$c = 0;
var_dump (isset($c)); // Will return TRUE

Case 4 :

var_dump (isset($d)); // Will return FALSE
//oops i did'nt assing the variable.

Hope this helped you .