PHP Basics Quiz

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Questions and Answers

Which of the following best describes the primary function of PHP?

Operating system level process handling.

Database management and query execution.

Server-side scripting for dynamic web content generation. (correct)

Client-side scripting for user interface interactions.

What is the purpose of the `<?php ?>` tags in HTML when using PHP?

To define CSS styles for the page.

To display standard HTML elements only.

To embed and execute Javascript code.

To enclose the PHP code within the HTML document. (correct)

Which of the following is not a typical task handled by PHP on a web page?

Accessing and manipulating data from databases.

Generating static HTML pages. (correct)

Processing user input from forms.

Creating different web pages based on user interaction.

In PHP, what is the purpose of a 'variable'?

To store and manage data of different types. (B) Signup and view all the answers

Which best describes MySQL?

An open-source relational database management system. (C) Signup and view all the answers

In a relational database, what is a 'table'?

A collection of related records with rows and columns. (A) Signup and view all the answers

Which of the following is the standard language used to interact with a MySQL database?

SQL (B) Signup and view all the answers

Which SQL statement is used to add new data to a table?

INSERT (D) Signup and view all the answers

In a MySQL table, what is a 'primary key' used for?

Uniquely identifying each row in a table. (A) Signup and view all the answers

What is the purpose of a 'foreign key' in the context of MySQL?

To establish relationships between tables. (C) Signup and view all the answers

What is the primary purpose of constraints in a database?

To control and ensure data integrity. (C) Signup and view all the answers

Which PHP extension is commonly used to establish a connection to a MySQL database?

mysqli (A) Signup and view all the answers

Which function is used to execute an SQL query after a database connection is established in PHP using mysqli?

mysqli_query() (C) Signup and view all the answers

What does the `mysqli_fetch_assoc()` function do in PHP when retrieving data from a MySQL query?

Fetches a single row as an associative array. (A) Signup and view all the answers

Which function is used to retrieve all rows from a MySQL result and store them in an associative array?

mysqli_fetch_all() (A) Signup and view all the answers

What is SQL injection?

A security vulnerability where malicious SQL code is inserted through user inputs. (B) Signup and view all the answers

Why is it important to sanitize user input before using it in SQL queries?

To prevent SQL injection attacks. (A) Signup and view all the answers

Why should developers avoid hardcoding database credentials directly in code?

It poses a significant security risk because the information might be exposed. (D) Signup and view all the answers

Which method is recommended for more secure database interactions compared to directly embedding user input into SQL queries?

Using prepared statements and parameterized queries. (B) Signup and view all the answers

After retrieving data from a database using PHP, what is an important step that should be performed?

Close the connection to the database. (B) Signup and view all the answers

Study Notes

PHP Basics

PHP (Hypertext Preprocessor) is a server-side scripting language embedded within HTML. It's used to create dynamic web pages and applications.
PHP code is executed on the server, and the results are sent to the user's web browser as static HTML.
Key features include:
- Interpreted language: Code is executed line by line.
- Support for various databases: PHP can interact with databases like MySQL.
- Server-side scripting: Dynamic content generation.
Common tasks PHP handles on a web page include:
- Processing user input: Handling form submissions.
- Accessing and manipulating data from databases: Retrieving and updating data.
- Generating dynamic content: Creating different web pages based on user interaction.
Essential syntax includes:
- <?php and ?> tags to enclose PHP code within HTML.
- Variables: Data storage using keywords like $name.
- Control structures: if, else if, else, for, while for conditional execution and loop iteration.
- Functions: Blocks of reusable code.
- Data types: String, integer, float, boolean.
Key concepts and aspects:
- Variables: Store data.
- Operators: Perform operations like arithmetic, comparison, and logical.
- Arrays: Store multiple values.
- Objects: Complex data structures.
- Error handling: Crucial for robust code.

MySQL Basics

MySQL is a popular open-source relational database management system (RDBMS). It stores data in tables.
Relational database organizes data using tables with rows and columns.
Data is structured with defined schemas to ensure data integrity for related data.
Key concepts:
- Database: A collection of related tables.
- Table: Data is organized in structured format with rows and columns.
- Row: A single record in a table (i.e., an entry).
- Column: Each attribute for a record. Defines the properties like name, date of birth etc.
SQL (Structured Query Language) is the standard language to interact with MySQL.
Key SQL commands:
- SELECT: Retrieves data from tables.
- INSERT: Adds new data to tables.
- UPDATE: Modifies existing data.
- DELETE: Removes data from tables.
- CREATE TABLE: Creates new tables.
- DROP TABLE: Deletes tables.
- ALTER TABLE: Modifies existing table structure.
Data types in MySQL:
- Integer, Varchar, Date, Float, etc.
Important aspects:
- Primary Key: Uniquely identifies each row in a table to enforce data integrity and ensure a unique identifier.
- Foreign Key: Establishes relationships between tables.
- Constraints: Used to control and ensure data integrity.

PHP interacting with MySQL

PHP can connect to and execute SQL queries against a MySQL database.
A connection to the database is established using PHP's database extension (e.g., mysqli).
SQL queries are executed using PHP's database functions.
Results from the SQL query can be processed and displayed to the user.
Key steps in the process of retrieving data, typically include:
- Establish a connection to the database.
- Use mysqli_query to execute SQL query.
- Fetch results from the query using functions such as mysqli_fetch_assoc or mysqli_fetch_all.
- Process the fetched data.
- Close the connection to the database when finished.
Error handling is vital for preventing crashes and giving useful feedback in situations like incorrect password or unable to connect to the db.

Example: Simple PHP code to retrieve data from MySQL

<?php
// Database credentials
$servername = "localhost";
$username = "your_username";
$password = "your_password";
$dbname = "your_database";

// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);

// Check connection
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}

// SQL query to select data
$sql = "SELECT id, name FROM users";
$result = $conn->query($sql);

// Check for results
if ($result->num_rows > 0) {
    // Output data of each row
    while($row = $result->fetch_assoc()) {
      echo "id: " . $row["id"]. " - Name: " . $row["name"]. "<br>";
    }
} else {
    echo "0 results";
}

$conn->close();
?>

This example retrieves data from a table named users.
Replace placeholders with your database credentials.
The mysqli_fetch_assoc fetches rows as associative arrays.

Security Considerations

Sanitize user input to prevent SQL injection attacks: Never directly embed user input into SQL queries.
Use prepared statements with parameterized queries for safer database interactions.
Secure database credentials: Store securely. Avoid using insecure methods like hardcoding them in the code.

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Description

Test your knowledge of PHP, the server-side scripting language used for dynamic web development. This quiz covers essential features, syntax, and common tasks associated with PHP programming. Assess your understanding of how PHP interacts with HTML and databases.