various way to check whether the value is set

gistfile1.aw

<?php
$subjects = array(
    null,
    true,
    false,
    "false",    // 文字列の false
    "",         // 空文字列
    0,          // integer の 0
    "0",        // string の 0
    "aaaaa",    // 任意のstring
    12345,      // 任意のinteger
    array(),    // 空の配列
);

foreach ($subjects as $subject) {
    $subject_str = str_replace("\n", '', var_export($subject, true));

    echo "*** {$subject_str} ***";

    echo "\nisset({$subject_str}): ";
    echo isset($subject) ? 'true' : 'false';

    echo "\n!empty({$subject_str}): ";
    echo !empty($subject) ? 'true' : 'false';

    echo "\n({$subject_str}): ";
    echo ($subject) ? 'true' : 'false';

    echo "\n\n";
}