Checking the Existence of an Array Element in PHP

Using isset you can check the existence of an array element:

<?php
	$arr = ['a', 'b', 'c'];
	
	if (isset($arr[5])) {
		echo $arr[5];
	} else {
		echo 'element does not exist';
	}
?>

You can also check an element of a non-existent array:

<?php
	if (isset($arr[5])) {
		echo $arr[5];
	} else {
		echo 'array or element does not exist';
	}
?>

Without running the code, determine what will be displayed on the screen:

<?php
	$test = 0;
	
	if (isset($test)) {
		echo '+++';
	} else {
		echo '---';
	}
?>

Without running the code, determine what will be displayed on the screen:

<?php
	$test = null;
	
	if (!isset($test)) {
		echo '+++';
	} else {
		echo '---';
	}
?>

Without running the code, determine what will be displayed on the screen:

<?php
	$test = null;
	
	if (isset($test)) {
		echo '+++';
	} else {
		echo '---';
	}
?>

Without running the code, determine what will be displayed on the screen:

<?php
	if (!isset($test)) {
		echo '+++';
	} else {
		echo '---';
	}
?>

Without running the code, determine what will be displayed on the screen:

<?php
	$test = '';
	
	if (isset($test)) {
		echo '+++';
	} else {
		echo '---';
	}
?>

Without running the code, determine what will be displayed on the screen:

<?php
	if (!isset($test)) {
		echo '+++';
	} else {
		echo '---';
	}
?>

Without running the code, determine what will be displayed on the screen:

<?php
	$test = false;
	
	if (isset($test)) {
		echo '+++';
	} else {
		echo '---';
	}
?>

Without running the code, determine what will be displayed on the screen:

<?php
	$arr = [1, 2, 3, 4, 5];
	
	if (isset($arr[])) {
		echo '+++';
	} else {
		echo '---';
	}
?>