What potential issues or errors can arise when attempting to combine multiple PHP scripts?

When combining multiple PHP scripts, potential issues can arise due to conflicting variable names, functions, or classes. To avoid these conflicts, it is important to properly namespace or encapsulate the code to prevent any naming collisions. Additionally, make sure to include the scripts in the correct order to ensure that dependencies are met.

// Example of encapsulating code to prevent naming conflicts
class Script1 {
    // Code from first script
}

class Script2 {
    // Code from second script
}