What are the differences between mysql_* functions and mysqli_* functions in PHP?

Introduction to mysql_* and mysqli_* Functions in PHP

PHP provides two sets of functions for interacting with MySQL databases: the older `mysql_*` functions and the newer `mysqli_*` functions. Understanding the differences between these two sets of functions is crucial for writing efficient and secure database interactions in PHP.

mysql_* Functions

The `mysql_*` functions are the original MySQL extension functions provided by PHP. They are used for interacting with MySQL databases but are now deprecated and have been removed in PHP 7.0.0 and later. The `mysql_*` functions were designed to provide basic MySQL database interaction capabilities, but they lack some of the features and security improvements of more recent alternatives.

Features of mysql_* Functions

• Simplicity: The `mysql_*` functions offer a straightforward way to perform database operations. They include functions such as `mysql_connect()`, `mysql_query()`, and `mysql_fetch_array()`.
• Limited Error Handling: Error handling with `mysql_*` functions is relatively basic. You use functions like `mysql_error()` to get error messages.
• No Support for Prepared Statements: The `mysql_*` functions do not support prepared statements, which are important for preventing SQL injection attacks.

Example

Consider the following example using `mysql_*` functions:

$link = mysql_connect("localhost", "user", "password");
mysql_select_db("database", $link);

$result = mysql_query("SELECT * FROM table");
while ($row = mysql_fetch_array($result)) {
    echo $row["column"];
}

This code connects to a MySQL database, selects a database, performs a query, and fetches the results.

mysqli_* Functions

The `mysqli_*` functions are an improved MySQL extension introduced with PHP 5.0. They provide a more robust and secure way to interact with MySQL databases compared to the old `mysql_*` functions. The `mysqli_*` functions offer enhanced features such as support for prepared statements, object-oriented interface, and improved error handling.

Features of mysqli_* Functions

• Support for Prepared Statements: `mysqli_*` functions support prepared statements, which help protect against SQL injection attacks. Functions like `mysqli_prepare()`, `mysqli_stmt_bind_param()`, and `mysqli_stmt_execute()` are used for this purpose.
• Object-Oriented Interface: In addition to the procedural interface, `mysqli_*` functions offer an object-oriented approach, which can be more intuitive and easier to manage.
• Enhanced Error Handling: Error handling with `mysqli_*` functions is more advanced, using methods like `mysqli_error()` and `mysqli_errno()` to provide detailed error information.

Example

Consider the following example using `mysqli_*` functions:

$link = new mysqli("localhost", "user", "password", "database");

$stmt = $link->prepare("SELECT * FROM table");
$stmt->execute();
$result = $stmt->get_result();
while ($row = $result->fetch_assoc()) {
    echo $row["column"];
}

This code connects to a MySQL database using the `mysqli` class, prepares a statement, executes it, and fetches the results.

Key Differences

• Deprecation: `mysql_*` functions are deprecated and removed in PHP 7.0.0, while `mysqli_*` functions are actively supported and recommended.
• Security: `mysqli_*` functions support prepared statements, which enhance security against SQL injection, unlike `mysql_*` functions.
• Features: `mysqli_*` functions offer more advanced features, including object-oriented interface and enhanced error handling.

Conclusion

When working with MySQL databases in PHP, it is essential to use `mysqli_*` functions due to their enhanced features and security improvements. `mysql_*` functions should be avoided as they are outdated and lack support in the latest versions of PHP.