How can isset() be used to check for the existence of a variable in PHP?

To check for the existence of a variable in PHP, you can use the isset() function. This function returns true if the variable exists and has a non-null value, otherwise it returns false. By using isset(), you can prevent errors that may occur when trying to access a variable that does not exist.

// Check if the variable $myVar exists
if (isset($myVar)) {
    echo "Variable exists!";
} else {
    echo "Variable does not exist!";
}