This set of PHP multiple choice questions and answers focuses on Object tools. It will be useful for anyone learning PHP Basics and Fundamentals.
1. Which function was introduced to help automate the inclusion of class files?
Explanation: When the PHP engine encounters an attempt to instantiate an unknown class, it invokes the __autoload() function, passing it the class name as a string. It is up to the implementer to define a strategy for locating and including the missing class file.
2. How many times can you define __autoload in a process?
d) as many times as needed
Explanation: __autoload is a powerful tool, but it does have some limitations. In particular, you can only define it once in a process. If you need to change your autoload function dynamically you should look at the spl_autoload_register function, which supports that functionality.
3. Which one of the following functions will you use to check that the class exists before you work with it?
Explanation: The class_exists() function accepts a string representing the class to check for and returns a Boolean true value if the class exists and false otherwise.
4. Which one of the following will you use to check the class of an object?
Explanation: This function accepts any object as an argument and returns its class name as a string.
5. PHP 4 did not support instanceof. Instead, which function did it provide?
Explanation: As of PHP 5.3 is_a() no longer deprecated.
6. You use the get_class_methods() function to return the names of all the methods in the class. Which function will you use to print it on the screen?
Explanation: The function get_class_methods returns an array therefore we cannot use echo.
7. If you call a method and it doesn’t exist it’ll cause a problem. To check the method which function will you use?
Explanation: There is another method which you can use – method_exists() for similar purpose.
8. What will be the output if a protected method is given as argument to the function method_exist()?
a) Method does not exist
Explanation: method_exists() returns true for private and protected methods as well as for public ones. Remember that the fact that a method exists does not mean that it will be callable.
9. Which one of the following function should I use to find the parent class of a class?
Explanation: The class functions also allow us to chart inheritance relationships.This function requires either an object or a class name, and it returns the name of the superclass, if any. If no such class exists, that is, if the class we are testing does not have a parent, then the function returns false.
10. Which class accepts a class name or an object reference and returns an array of interface name?
Explanation: is_subclass_of() will tell you only about class inheritance relationships. It will not tell you that a class implements an interface.
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