isset-null-value.php

<?php

// Interestingly, a null value in an isset() check will return false

$r = array(
    "a" => 1,
    "b" => null
);

echo "a: ".(isset($r['a']) ? 'Yes' : 'No').PHP_EOL;
echo "b: ".(isset($r['b']) ? 'Yes' : 'No').PHP_EOL;
echo "c: ".(isset($r['c']) ? 'Yes' : 'No').PHP_EOL;

/*
 * $ php a.php
 * a: Yes
 * b: No
 * c: No
 */