php isset函数的用法举例

<?
if ( (! isset ($PHP_AUTH_USER)) || (! isset ($PHP_AUTH_PW)) ):
     header('WWW-Authenticate: Basic realm="Secret Family"');
     header('HTTP/1.0 401 Unauthorized');
     print "Authorization is required.";
     exit;
endif;
?>

<?
    $foo = 1;
    if (isset($foo)) {
            echo "Foo is setn";
    } else {
            echo "Foo is not setn";
    }

    if (isset($bar)) {
            echo "Bar is setn";
    } else {
            echo "Bar is not setn";
    }
?>

<?php
setcookie("username","michele");
echo 'Cookie created.';

if (!isset($_COOKIE['username'])){
    echo ("Oops, the cookie isn't set!");
}else{
    echo ("The stored username is ". $_COOKIE['username'] . ".");
}
?>

<?php
$array = array('a' => 'R', 'b' => 2, c => '2');
print "<p>Using for:</p>n<p>";
$limit = count($array);
for($i = 0; $i < $limit; $i++)
    if( isset($array[$i]) )
        printf("&middot; %s,", $array[$i]);
?>