In the context of PHP programming, why is it important to differentiate between built-in PHP functions like dir and custom functions within a script?

It is important to differentiate between built-in PHP functions like dir and custom functions within a script to avoid naming conflicts. If a custom function is named the same as a built-in function, it can lead to unexpected behavior and errors in the script. To solve this issue, always use unique names for custom functions to prevent any clashes with existing PHP functions.

// Incorrect usage - naming conflict with built-in function dir
function dir($path) {
    // Custom function logic
}

// Corrected usage - using a unique name for the custom function
function list_directory($path) {
    // Custom function logic
}