PHP Set 8

Question 1

What does a child class inherit from its parent class?

Answer 1

All public and protected properties and methods

Question 2

How is an inherited class defined?

Answer 2

Using the extends keyword
Ex: class Apple extends Food { }

Question 3

How can an inherited method be overridden in a child class?

Answer 3

By redefining a method using the same name in the child class

Question 4

How can method overriding or class inheritance be prevented?

Answer 4

Using the final keyword prevents child classes from being made from an object or a method being redefined

Question 5

What is an abstract class?

Answer 5

A class that has at least one abstract method

Question 6

What is an abstract method?

Answer 6

A method that is declared with the abstract keywork and not implemented in code

Question 7

What is the syntax for declaring an abstract function?

Answer 7

abstract function name($param): returntype;

Question 8

What are the rules for when a child class is inherited from an abstract class?

Answer 8

1. The child class method must be defined with the same name and redeclare the parent abstract method
2. The child class method must be defined with the same or a less restricted access modifier
3. The number of required arguments must be the same but the child class can add optional arguments

Question 9

What is the difference between an interface and an abstract class?

Answer 9

1. Interfaces cannot have properties but abstract classes can
2. All interface methods are abstract so they abstract keyword isn’t necessary
3. All interface methods must be public
4. Classes can implement an interface and inherit from another class at the same time

Question 10

How do you declare an interface and how do you implement one?

Answer 10

Declare:
interface Animal {
functions
}
Implement:
class Cat implements Animal { }

Question 11

What are the 2 methods used to connect to MySQL?

Answer 11

1. MySQLi extension
2. PDO (PHP Data Objects)

Question 12

What is the main difference between MySQLi and PDO?

Answer 12

PDO supports various databases but MySQLi only supports MySQL
MySQLi is a but faster
PDO supports 12 different drivers but MySQLi only supports MySQL

Question 13

How do you open a MySQL connection using MySQLi?

Answer 13

$conn = new mysqli(“localhost”, “username”, “password”, “dbName”)

Question 14

How do you open a MySQL connection using PDO?

Answer 14

$conn = new PDO($dsn, “root”, “lsucceed168”, $options)
where $dsn = “mysql:host=localhost;dbname=name;charset=utf8mb4”

Question 15

How do you create a table in MySQL?

Answer 15

With the CREATE TABLE statement
$sql = “CREATE TABLE MyGuests (id INT(6) UNSIGNED AUTO_INCREMENT PRIMARY KEY,
firstname VARCHAR(30) NOT NULL, lastname VARCHAR(30) NOT NULL, email VARCHAR(50),
reg_date TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP )”;

Question 16

How do you perform an insert to a table in MySQL?

Answer 16

With the INSERT INTO statement
$sql = “INSERT INTO MyGuests (firstname, lastname, email) VALUES (‘John’,
‘Doe’, ‘john@example.com’)”;

Question 17

What is the difference between MySQLi and PDO when detecting command errors?

Answer 17

With MySQLi you can check the return value in an if statement
With PDO you have to use a try-catch block to detect errors

Question 18

What is a MySQL prepared statement?

Answer 18

A technique used to execute the same or similar SQL statements repeatedly with high efficiency

Question 19

What are the procedures for creating a prepared MySQL statement?

Answer 19

1. Prepare: create an SQL query with empty values as placeholders with a question mark or variable name
2. Bind: Bind values or variables to the placeholders
3. Execute the query simultaneously

Question 20

What is the syntax to execute a prepared statement with MySQLi?

Answer 20

$sql = $conn->prepare(“INSERT INTO
myguests(firstname, lastnamen,
email) VALUES (?, ?, ?)”);
$sql->bind_param(“sss”, $fn, $ln,
$email); // “sss” means that $fn, $ln
and $email as a string
$fn = “Mary”;
$ln = “Gao”;
$email = “mary_gao@gmail.com”;
$sql->execute();

Question 21

What are the benefits of using prepared SQL statements?

Answer 21

1. They are useful against SQL injection attacks
2. They reduce parsing time as the preparation of the query is only done once when the same statement is needed repeatedly
3. Minimize server bandwidth as you need to send only the parameters each time and not the whole statement

Question 22

What data types can be passed in when using bind_param?

Answer 22

i for integer
d for double
s for string
b for binary large object

Question 23

What is the syntax to execute a prepared statement with PDO?

Answer 23

$stmt = $conn->prepare(“INSERT INTO
MyGuests (firstname, lastname,
email)
VALUES (:firstname, :lastname,
:email)”);
$stmt->bindParam(‘:firstname’,
$firstname);
$stmt->bindParam(‘:lastname’,
$lastname);
$stmt->bindParam(‘:email’, $email);
$firstname = “Mary”;
$lastname = “Gao”;
$email = “mary.gao@example.com”;
$stmt->execute();

Question 24

What are the other differences between MySQLi and PDO?

Answer 24

1. PDO allows for named parameters but with MySQLi you can only use ?
2. PDO does not allow using named and positional parameters in the same query