How can unexpected errors like missing variables be prevented in PHP code?

To prevent unexpected errors like missing variables in PHP code, it is important to check if the variable exists before using it. This can be done using functions like isset() or empty() to verify if a variable has been set and has a non-null value before proceeding with the operation that requires it.

// Check if the variable exists before using it
if(isset($variable)) {
    // Proceed with using the variable
    echo $variable;
} else {
    // Handle the case where the variable is missing
    echo "Variable is missing";
}