<?php
$var = 'false';
if ($var) {
echo 'variable value is: true';
} elseif (!isset($var)) {
echo 'variable is not set';
} elseif ($var == false) {
echo 'variable value is: false';
} elseif ($var === false) {
echo 'variable is set to false';
} elseif ($var == true) {
echo 'variable is set';
} elseif ($var === true) {
echo 'variable is set to true';
}