<?php
$test = array();
$test['eval_zero'] = 0;
$test['eval_null'] = null;
$test['eval_false'] = false;
$test['eval_true'] = true;
if (isset($test['eval_zero'])) echo 'Zero is set.';
if (!empty($test['eval_zero'])) echo 'Zero is not empty.';
if (isset($test['eval_null'])) echo 'NULL is set.';
if (!empty($test['eval_null'])) echo 'NULL is not empty.';
if (isset($test['eval_false'])) echo 'False is set.';
if (!empty($test['eval_false'])) echo 'False is not empty.';
if (isset($test['eval_true'])) echo 'True is set.';
if (!empty($test['eval_true'])) echo 'True is not empty.';
Zero is set.False is set.True is set.True is not empty.
Output for 8.3.5
Warning: PHP Startup: Unable to load dynamic library 'sodium.so' (tried: /usr/lib/php/8.3.5/modules/sodium.so (libsodium.so.23: cannot open shared object file: No such file or directory), /usr/lib/php/8.3.5/modules/sodium.so.so (/usr/lib/php/8.3.5/modules/sodium.so.so: cannot open shared object file: No such file or directory)) in Unknown on line 0
Zero is set.False is set.True is set.True is not empty.