Interview Questions for Fresher Set-9

81) What is the difference between session_unregister() and session_unset()?
The session_unregister() function unregister a global variable from the current session and the session_unset() function frees all session variables.

82) When do sessions end?

Sessions automatically end when the PHP script finishes executing but can be manually ended using the session_write_close().

83) What is the meaning of a Persistent Cookie?

A persistent cookie is permanently stored in a cookie file on the browser's computer. By default, cookies are temporary and are erased if we close the browser.

84) How can you propagate a session id?

You can propagate a session id via cookies or URL parameters.

85) How to initiate a session in PHP?

The use of the function session_start() lets us activating a session.

86) what is the definition of a session?

A session is a logical object enabling us to preserve temporary data across multiple PHP pages.

87) What is faster?

1- Combining two variables as follows:

$variable1 = 'Hello ';

$variable2 = 'World';

$variable3 = $variable1.$variable2;

Or

2- $variable3 = "$variable1$variable2";

$variable3 will contain "Hello World". The first code is faster than the second code especially for large large sets of data.

88) What's the difference between __sleep and __wakeup?

__sleep returns the array of all the variables that need to be saved, while __wakeup retrieves them.

89) Are Parent constructors called implicitly inside a class constructor?

No, a parent constructor have to be called explicitly as follows:

parent::constructor($value)

90) In PHP, objects are they passed by value or by reference?

In PHP, objects passed by value.