isset() usage
Example 1:
$post['var'] = 100;
isset($post[‘var’]) will return true
Example 2:
isset($name) will return false if $name has not been declared
Example 3:
$post['v1'] = 100;
isset($post[‘v2’]) will return false
since isset is not assigned
empty()
It essentially means
!isset($var) || $var == false.
So it is either is not set or it is set but its value is false
Example 1
$post['v1'] = 100;
empty($post[‘v1’]) is false
Example 2
$post['v2'] = false
empty($post[‘v2’]) is true
Example 3
empty($post[‘v3’]) is true because $post[‘v3] has not been declared