If we try to copy a referenced object, it will simply point back to the addressing location of the original object. To remedy the problems with copying, PHP offers an explicit means for cloning an object which is known as object cloning.

Ans: In PHP an extended class is always dependent on a single base class that is multiple inheritances is not supported. Classes are extended using the keywords ‘extends’

When a specified error (exceptional) condition occurs in the script is called an exception.
There are Four important keywords of exceptions:
Try
Catch
Throw
Finaly

Configuration directive scopes are given bellow:
PHP_INI_PERDIR: Directive can be modified within the php.ini,httpd.conf, or .htaccess files.
PHP_INI_SYSTEM: Directive can be modified within the php.ini and httpd.conf files.
PHP_INI_USER: Directive can be modified within user scripts.
PHP_INI_ALL: Directive can be modified anywhere.

Public: Public declared items can be accessed everywhere.

Protected: Protected limits access to inherited and parent classes (and to the class that defines the item).

Private: Private limits visibility only to the class that defines the item.

Static: A static variable exists only in a local function scope, but it does not lose its value when program execution leaves this scope.

Final: Final keyword prevents child classes from overriding a method by prefixing the definition with final. It means if we define a method with final then it prevent us to override
the method.

transient: A transient variable is a variable that may not be serialized.

volatile: A variable that might be concurrently modified by multiple threads should be declared volatile. Variables declared to be volatile will not be optimized by the compiler because their value can change at any time