Are you getting tense over your upcoming PHP oops interview questions?
Then not anymore. Prep yourself beyond the qualifying mark with the best sample question answers and interview tips from our top PHP developers.
Most commonly asked in a PHP oops interview questions are regarding a developer’s experience and testing his communication and management skills. Therefore, one must have in-depth knowledge about PHP while sitting for such interviews.
What is a PHP Object-Oriented Programming-Based Career?
PHP is an acronym for PHP hypertext preprocessor widely used as an open-source, object-oriented programming language.
It is specially designed for creating dynamic websites and mobile APIs. It is the best career to enter the job market at the current time. Usually, any PHP is qualified through interviews rather than merit. There are various advantages of object-oriented programming over procedural programming:
- First, OOP is a more efficient and straightforward method of programming. The programmes have a clear structure, thanks to OOP.
- Second, OOP helps keep PHP code DRY (Don’t Repeat Yourself), making it easier to maintain, alter, and debug.
- Third, OOP allows developers to design whole reusable applications with less code and less time.
Let’s pretend we have a Fruit class. Fruit can have characteristics such as name, colour, weight, and so on. So $name, $colour, and $weight are variables that can be used to store the values of these characteristics.
When the individual objects (apple, banana, etc.) are formed, they inherit all of the class’s attributes and behaviors, but the values for the properties will be different for each object. Let’s pretend we have a Fruit class. A fruit can have characteristics such as name, colour, weight, and so on. $name, $colour, and $weight are variables that can be used to store the values of these characteristics.
When the individual objects (apple, banana, etc.) are formed, they inherit all of the class’s attributes and behaviors, but the values for the properties will be different for each object.
While preparing for PHP oops interview questions they can be subdivided into three sections.
- Beginner label PHP oops interview questions
- Intermediate label PHP oops interview questions
- Advanced level PHP oops interview questions
Without doing any for the delay let’s jump in.
Top 30 Basic PHP Developer Interview Questions
1. What is oops and what are its basic concepts with their definitions? (High order thinking PHP oops interview questions)
Oops is an acronym form of object-oriented programming system where programs are treated as an object collection and each object is just an instance of a class. There are four kinds of concepts mentioned under Oops. They are-
- Abstraction – is a concept in object-oriented programming that “shows” only the most important features while “hiding” the rest. The basic goal of abstraction is to keep users from having to deal with extraneous details…. It is one of the most crucial OOP ideas.
- Encapsulation – is a concept within the study of oops that is regarded as an attribute of an object. It contains all kinds of hidden data within it and this data can be restricted to the members of that class. Different types of levels found in encapsulation are Public, Protected, and Private, internal, and protected internal.
- Inheritance – is a concept under PHP objects-oriented programming. This is where one class shares the structure and behavior that is described by another class. This is again subdivided into two forms-
- If the inheritance is in one class then it is known as single inheritance
- If the inheritance is depending upon multiple classes then it is known as multiple inheritances.
- polymorphism – is described as assigning behavior or value in a subclass to something already declared in the main class. In other simple words, polymorphism means taking more than one form.
2. What do you mean by a class and what is the difference between an object and a class? [Most frequently asked PHP oops interview questions]
A class is considered as a representation of a particular type of object. It is a template that describes the details of that object. An abstract class is one that cannot be instantiated. Abstract class does not facilitate creating an object, but these objects can be inherited. Only an abstract methodology helps in the creation of an abstract class.
The computer language only allows abstract methodology in creating abstract classes, while other languages consist of both non-abstract and abstract in their abstract class.
The object is a smaller subunit of class. Objects hold the actual multiple information whereas classes don’t have any kind of information.
Definition of properties and functions are performed in a class and are used by the object. A class can be subdivided while an object cannot be. It is not possible to create an instance of an abstract class.
3. The difference between final class and final method [Beginner level PHP oops interview questions]
The final keyword used in a method declaration represents that any subclass cannot override the said step. At the same time, a class that is declared as final cannot consist of any subclass.
These terms are advantageous in the creation of an immutable class such as a string class. Except for classes and methods, no other entities such as properties can be declared as final.
4. What do you mean by an object in PHP and what are the different kinds of PHP variables in object-oriented programming? [Most frequently asked PHP oops interview questions]
An object is an instance of a particular class that has its behavior state and identity.
There are 8 data types in total within the study of PHP variables. They are as follows :
- Integers– any kind of the whole number without any decimal point. for example 5162
- Double-these are the floating numbers that can consist of decimal points. for example 41.1
- Boolean -these are the data types that have two possible values that are false or true.
- NULL– it is a special data type that has only one value assigned to it.
- Strings-these are the sequences of characters
- Arrays– these data types are named and indexed collection of various values.
- Object– these are the data types that are instances of programmer-defined classes that can package other values and functions specific to the class.
- Resources– These are data types with special variables that can hold references to any external resources to PHP.
5. What is a constructor, manipulator and destructor? [Most frequently asked PHP oops interview questions]
A constructor is a methodology that is used to initialize a state of an object. It is initiated at the time of the creation of an object. The two basic rules for construction are
- Constructor names should always be mentioned according to the same class name.
- There should be no return type in a constructor.
Manipulator is described as functions used in conjunction with the insertion and extraction operator on the object.
A destructor is a methodology that automatically is called on when the object is made up of scope or destroyed. Destructor name should also be mentioned as the same class name but a tilde symbol before its name.
6. Define the term virtual function and friend function? [High order thinking PHP oops interview questions]
A virtual function is described as a member function of a class. The functionality of the virtual function can be overridden from its derived class. The function is initiated by using a Keyword called virtual and it is given at the time of function declaration.
This function is declared when using a token in C ++. It can also be achieved in C++ and Python by using different function pointers to the function.
A friend function is a class that is allowed for access to any public, private, or protected data provided that it is within the same class. If this function is defined beyond the class there, it cannot access such information.
A friend function is declared anywhere during the class declaration. Thus, the friend function is not affected by access control keywords such as private, public, or protected.
7. What is considered as a function overloading and operator overloading? [High order thinking PHP oops interview questions]
Function overloading is a type of regular function that can carry out different kinds of tasks. This function allows the creation of several steps with the same name that differ from each other by the type of input and output of the function. A small example for this instant is
Void add(int& a, int& b);
Void add(double& a,double& b, );
Void add(struct bob& a,struct bob& b, );
[This is an ideal way to answer this oops interview question in particular. However, you can answer in your own words after understanding the core matter from the given answers.
The term operator overloading means a function where various operators are applied depending on the arguments. For example, an operator such as ‘-‘ and ‘*’ is used to pass through a function along with its presidents to execute.
8. What does the term ternary operator mean? [Beginners PHP oops interview questions]
It is an operator that takes three arguments. These arguments are of different data types depending on the function. It is also often termed a conditional operator.
9. What is the function of the finalize method? [Most frequently asked PHP oops interview questions]
Finalize method helps to clean up the resources that are not currently in use. It is protected and thus accessible only through to the same class or a derived class.
10. Mention different kinds of arguments. [Beginner PHP oops interview questions]
A variable is used at the time of declaration of a function or a subroutine. The arguments follow the body of the function by matching the defined variable. An argument can be of two types namely-
- Call by Value arguments
- Call by Reference arguments
11. What is the function of super keyword? [Beginner PHP oops interview questions]
The super keyword is used to insert an overridden method that overrides one of its superclass steps. This feature allows accessing various overridden methods and hidden members of the superclass. It is also used to forward a call from a constructor to a different constructor in the superclass.
12. What do you mean by method overriding? Differentiate between overloading and overriding. [Most frequently asked PHP oops interview questions]
Method overriding allows a subclass to command the implementation of a method that can override in the main class. The implementation thus given will override by the same method name, same variable, and same return type.
Overloading is a Static Binding that has the same method with different arguments. This may or may not return the equal value within the same class on its own. Why overriding is a dynamic binding process with the same method names with the same arguments and return type associated with the class and its subclass.
[This is an ideal way to answer this PHP oops interview question in particular. However, you can answer in your own words after understanding the core matter from the given answers]
13. What is the function of an interface? [Most frequently asked PHP oops interview questions]
It is a collection of abstract methods. By implementing an interface a class can inherit all the Abstract methods contained within that particular interface. Java mainly uses this kind of interface to implement multiple inheritances.
14. What do you mean by exception handling? [Beginner PHP oops interview questions]
An exception is a situation that arises during the execution of any program. These are of two types-runtime exception and error exceptions. These exceptions are handled through 3 exception handling mechanisms-try, catch and throw keywords.
15. What do you mean by tokens? [Beginner PHP oops interview questions]
A token is usually recognized through a compiler where it can’t be broken down to component elements. Few examples of tokens are keywords identifiers, string literals and operators.
Tokens also consist of punctuation characters such as brackets, braces, commas and parentheses.
16. What do you mean by access modifiers? [Beginner PHP oops interview questions]
Access modifiers are the feature that is used to determine the scope of the method or variable that is accessed from various objects or classes. There are mainly five kinds of access modifiers namely-
- private
- Protected
- public
- friend
- Protected friend.
17. What is the function of a pure virtual function? give an example. [High order thinking PHP oops interview questions]
A pure virtual function is an undefined function that can be overridden within the derived class. Any virtual function can be declared as pure by using the operator sign of =0.
For example
1virtual void function () // virtual . Not pure
2
3 virtual Void function () = 0 // pure virtual
[This is an ideal way to answer this oops interview question in particular. However, you can answer in your own words after understanding the core matter from the given answers]
18. State all the operators which cannot be overloaded. [Beginner PHP oops interview questions]
Three types of operators cannot be overloaded. They are as follows
- Scope resolution
- members selection
- member selection through a pointer to a function
19. What do you mean by Static Binding? [Most frequently asked PHP oops interview questions]
Starting winding is the association of a name with a particular class. This type of binding takes place where our name can be associated with the class at the time of compilation. It is also popularly known as early binding.
20. Give examples of constants in PHP along with their purpose. [Most frequently asked PHP oops interview questions]
- LINE– this constant represents the current line number of a file
- FILE– this constant represents the full path and file name of a particular file. In case it is used within and includes the name of the included file is returned
- FUNCTION – this is used to represent the name of the function
- CLASS– this is used to represent the class name as it was assigned
- METHOD -it is used to represent the class method name
Intermediate and Advanced Level PHP Developer Interview Questions.
21. What is the meaning of NULL? [High order thinking PHP oops interview questions]
A special type of data that can have only a single assigned value is known as NULL. In the case of variable data type null, it has no value assigned to it. It can be represented as follows-
1 $var = NULL;
If the special constant NULL is capitalized then the case is considered insensitive. You can also assign it as
1 $var = null;
Following are the properties of the variable assigned through NULL value
- It determines to FALSE in a Boolean context
- While testing with the IsSet() function, it returns FALSE.
22. State the differences between PHP constant and variable in object-oriented programming. [intermediate PHP oops interview questions]
Constant
- It is not necessary to mention the Dollar sign before the constant
- They can be defined only by using the define() function.
- They may be accessed and assigned anywhere without any regard to variable scoping.
- Constant can never be redefined or undefined
Variables
- The Dollar sign must be mentioned while writing a variable
- Variable has to be defined by a simple assignment
- In PHP by default functions can only create and use variables within their scope.
- For each path, the variable can be redefined individually.
[This is an ideal way to answer this oops interview question in particular. However, you can answer in your own words after understanding the core matter from the given answers
23. When should you use=== in place of ==?[High order thinking PHP developer interview questions]
If the developer wants to check for a certain type, example integer or Boolean, the === will perform exactly the expected task from a strong type language. Whereas == word converts a type of data temporarily while trying to match with both operands types.
The Identity operator represented by === performs better because of not having to deal with any type of conversion. In case of inspections of variables for true/ false, the developers should avoid using == as this will take into account 0/1 and other similar kinds of representations.
24. What are the PSR standards you usually follow and why should you follow them? [Most frequently asked PHP oops interview questions]
PSR should be followed because coding standards always tend to vary between developers and companies. Therefore, issues can arise while reviewing another developer’s code and finding a code structure that is very different from your own.
In such cases, the PSR standard helps to determine the expectation of how the code should look like. This is done by eradicating all kinds of confusion and in some special cases, Syntax error too.
25. What are the three scope levels available in a PHP? Define them. [Most frequently asked PHP interview questions]
The 3 scope levels are as follows-
- Private- this quote is only visible to its class
- Public- this scope is visible to any kind of code that is accessing that particular class
- This is only visible to parent classes and the classes that are extended from the current class.
26. How can one prevent the following warning-” warning; cannot modify header information headers already sent”? Also mention when this occurs.
In this answer, the candidate appearing in the PHP oops interview questions should not output anything into the browser using a course that modifies HTTP headers.
Once the interviewer causes echo or any other code that clears the buffer then the developer can no longer set cookies or headers into it. This is also true regarding error messages full stop in the case where an error happens before the header command is used then the directive display-error is set.
27. What types of rules are considered to determine the “truth” of any value that is not already because of Boolean type? [Most frequently asked PHP oops interview questions]
Here is the list of rules that are used to determine the truth of any value that is not already of Boolean type
- If the value is in the form of a number then it is false in the case where it is exactly equal to zero and true otherwise.
- In the case where the value is a string then it is considered false if the string is empty.
- If the value is in the form of an Array then it is false if it contains no other values and it is considered true otherwise. In the case of objects containing a value means having a member variable that has already been assigned a certain value.
- Values for any NULL function are always false.
- Every valid resource provided are always true
- Never use double as Boolean
28. Mention the characteristics and respective rules necessary for naming a PHP variable?
Important characteristics of PHP variables are as follows
- All variables in PHP are denoted after writing a Dollar sign
- The value of the variable is assigned according to its most recent assignment
- Variables are assigned with operators where the variable is on the left-hand side and expression is evaluated on the right-hand side.
- Variables do not need to be declared before the assignment.
- Variables mentioned in PHP do not consist of intrinsic type- it means that a variable does not know in advance whether that will be used to store a number or a string of characters.
- Default values are assigned to the variable that is used before the assignment.
Two main rules need to be followed while naming a PHP value. They are as follows-
- Every variable name must start with a letter or an underscore character
- A variable name can be made up of numbers, letters and underscores. However, the use of characters like+,-,%,(,),&, etc. is strictly prohibited.
29. State the differences between PHP4 and PHP5. [High order thinking PHP developer interview questions]
PHP 4
- All the constructors are assigned with the same name as the class.
- Everything in PHP4 requires a value
- It does not specify any class as an abstract
- It does not consist of any static methods and properties in its class.
PHP5
- Constructors are usually termed as_construct and destructors are named as _destruct()
- Objects mention in PHP5 are passed through references
- It allows assigning a particular class as an abstract class
- It allows the use of static methods and properties in its class
[This is an ideal way to answer this oops interview question in particular. However, you can answer in your own words after understanding the core matter from the given answer.
30. Mention the method through which PHP and JavaScript and PHP and HTML could interact with each other? [High order thinking PHP oops interview questions]
PHP and Javascript can never directly interact with each other. This is mainly because PHP is a server-side language while Java is a client-side language. However, an interaction can be formed if we exchange the variable in such a way that PHP can generate JavaScript code to be executed by the browser. This method makes it possible to pass specific variables back to PHP through the URL.
A PHP script can generate desired HTML and also it is possible to pass information from HTML back to PHP. As PHP is a server-side language while HTML is a client-side language, PHP works on the server-side and interprets its result in the form of a string, array, or object. Then these results are used to display the values in HTML.
Conclusion
This brings us to the end of our practice PHP oops interview questions and answers blog. We hope that you can prepare yourself better with these object-oriented programming questions. Candidates are highly recommended to understand the purpose of the question asked during the interview before attempting.
Think twice before you give a final answer to any question regarding PHP. Keeping these things in mind and with a little cautious attitude you can nail any PHP oops interview questions. We sincerely hope that our recommended questions provided you with the necessary guidance for your upcoming interviews.
For more information related to world web applications with PHP feel free to check out our related articles.
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