What are common issues that can arise when using include() and new in PHP scripts?

One common issue that can arise when using include() in PHP scripts is that the included file may not be found or may contain errors, leading to a fatal error. To solve this, you can use the include_once() function instead, which will include the file only once and prevent any errors caused by multiple inclusions. Another common issue is when using the new keyword to create an instance of a class that does not exist or is not properly defined, resulting in a fatal error. To solve this, you should make sure that the class is properly defined before using the new keyword to create an instance of it.

// Using include_once() to prevent errors caused by multiple inclusions
include_once('file.php');

// Making sure the class is properly defined before creating an instance
if (class_exists('ClassName')) {
    $object = new ClassName();
} else {
    echo "Class ClassName is not properly defined.";
}