Do these ternary operator output the same result?

Question

Is $time ?: 3600 equivalent to isset($time) ? $time : 3600 ?

Thank you all.

Answer 1

No. There are cases for which they evaluate to the same value, but they are not equivalent.

<?php
print $time ?: 3600;
print "\n";
print isset($time) ? $time : 3600;
print "\n\n";

$time = 0;
print $time ?: 3600;
print "\n";
print isset($time) ? $time : 3600;
print "\n\n";

$time = 30;
print $time ?: 3600;
print "\n";
print isset($time) ? $time : 3600;
print "\n\n";
?>

Output:

PHP Notice:  Undefined variable: time in /home/hq6/PHP/Test2.php on line 2
3600
3600

3600
0

30
30