php - What is the best way to know is $_GET['example']=="somevalue"? -

if((isset($_get[example]))&&($_get['example']=='somevalue')){ ... } 

or

if((!empty($_get[example]))&&($_get['example']=='somevalue')){ ... } 

or just

if($_get['example']=='somevalue'){ ... } 

i asking why have seen many example people check first if $_get['example'] set , if $_get['example']=='somevalue' ( first , second example above ). don't understand why not use last solution ( if $_get['example']=='somevalue' $_get['example'] set ).

this question refers other variable ( $_post, $_server, ecc ).

if((isset($_get[example]))&&($_get['example']=='somevalue')){ ... } 

is right one, want know "variable" exists (or set) in order use it. empty checks wether has data of kind or not. example:

<?php $foo= 0;  if (empty($foo)) { // true because $foo empty     echo '$foo either 0, empty, or not set @ all'; }  if (isset($foo)) { // true because $foo set     echo '$foo set though empty'; }  if (isset($var)) { // false because $var not declared before    ... } ?>