How can the issue of accessing undefined variables be resolved in PHP scripts, especially within if-else constructs?

When accessing undefined variables in PHP scripts, it can lead to warnings or errors. To resolve this issue, you can use the isset() function to check if a variable is set before accessing it within if-else constructs. This helps prevent errors and ensures that your code runs smoothly without any unexpected issues.

// Example of using isset() to check if a variable is set before accessing it
$variable;

if(isset($variable)) {
    // Variable is set, so it can be safely accessed here
    echo $variable;
} else {
    // Variable is not set, handle this case accordingly
    echo "Variable is not set.";
}