You can prevent a class from overriding in C# by using the sealed keyword; whereas, the NotInheritable keyword is used to prevent a class from overriding in Visual Basic.

As far PHP concern it only support single Inheritance in scripting. we can also use interface to achieve multiple inheritance.

unlink()-deletes the given file from the file system.
unset() -makes a variable undefined.

1 : InnoDB provides us row level locking while MyISAM provides us table level locking.

2 : InnoDB offers foreign key constraints wheres in MyISAM does not have foreign key constraints.

3 : InnoDB does not have full text search wheres MyISAM provides us full text search.

CONSTRUCTOR : PHP allows developers to declare constructor methods for classes. Classes which have a constructor method call this method on each newly-created object, so it is suitable for any initialization that the object may need before it is used.

DESTRUCTORS : PHP 5 introduces a destructor concept similar to that of other object-oriented languages, such as C++. The destructor method will be called as soon as all references to a particular object are removed or when the object is explicitly destroyed or in any order in shutdown sequence.

strstr() returns part of a given string from the first occurrence of a given substring to the end of the string.
For example:
strstr("user@example.com","@") will return "@example.com".

stristr() is idential to strstr() except that it is case insensitive.

include()
The include() function takes all the content in a specified file and includes it in the current file. If an error occurs, the include() function generates a warning, but the script will continue execution.

include_once()
File will not be included more than once. If we want to include a file once only and further calling of the file will be ignored then we have to use the PHP function include_once().

require()
The require() function is identical to include(), except that it handles errors differently. The require() generates a fatal error, and the script will stop.

require_once()
The required file is called only once when a page is open and further calling of the file will be ignored.

On the server side, the main difference between GET and POST is where the submitted is stored. The $_GET array stores data submitted by the GET method. The $_POST array stores data submitted by the POST method.

On the browser side, the difference is that data submitted by the GET method will be displayed in the browser’s address field. Data submitted by the POST method will not be displayed anywhere on the browser.

GET method is mostly used for submitting a small amount and less sensitive data.
POST method is mostly used for submitting a large amount or sensitive data.