What is the purpose of using isset in PHP variables and what potential pitfalls can arise when implementing it?

The purpose of using isset in PHP variables is to check if a variable is set and is not NULL. This is useful to avoid errors when trying to access variables that may not have been defined or initialized. One potential pitfall when implementing isset is that it only checks if a variable is set, but not if it has a valid value. This means that a variable could be set to an empty string or 0, which isset would still consider as set.

// Check if a variable is set and not empty
if(isset($variable) && $variable !== ''){
    // Variable is set and not empty, do something with it
    echo $variable;
} else {
    // Variable is either not set or empty
    echo "Variable is not set or empty";
}