With PHP, you can connect to and manipulate databases.
MySQL is the most popular database system used with PHP.
WHAT IS MYSQL?
- MySQL is a database system used on the web
- MySQL is a database system that runs on a server
- MySQL is ideal for both small and large applications
- MySQL is very fast, reliable, and easy to use
- MySQL uses standard SQL
- MySQL compiles on a number of platforms
- MySQL is free to download and use
- MySQL is developed, distributed, and supported by Oracle Corporation
- MySQL is named after co-founder Monty Widenius's daughter: My
The data in a MySQL database are stored in tables. A table is a collection of related data, and it consists of columns and rows.
Databases are useful for storing information categorically. A company may have a database with the following tables:
- Employees
- Products
- Customers
- Orders
PHP + MYSQL DATABASE SYSTEM
- PHP combined with MySQL are cross-platform (you can develop in Windows and serve on a Unix platform)
DATABASE QUERIES
A query is a question or a request.
We can query a database for specific information and have a recordset returned.
Look at the following query (using standard SQL):
SELECT LastName FROM Employees
The query above selects all the data in the "LastName" column from the "Employees" table.
PHP 5 and later can work with a MySQL database using:
- MySQLi extension (the "i" stands for improved)
- PDO (PHP Data Objects)
Earlier versions of PHP used the MySQL extension. However, this extension was deprecated in 2012.
SHOULD I USE MYSQLI OR PDO?
If you need a short answer, it would be "Whatever you like".
Both MySQLi and PDO have their advantages:
PDO will work on 12 different database systems, where as MySQLi will only work with MySQL databases.
So, if you have to switch your project to use another database, PDO makes the process easy. You only have to change the connection string and a few queries. With MySQLi, you will need to rewrite the entire code - queries included.
Both are object-oriented, but MySQLi also offers a procedural API.
Both support Prepared Statements. Prepared Statements protect from SQL injection, and are very important for web application security.
MYSQL EXAMPLES IN BOTH MYSQLI AND PDO SYNTAX
In this, and in the following chapters we demonstrate three ways of working with PHP and MySQL:
- MySQLi (object-oriented)
- MySQLi (procedural)
- PDO
MYSQLI INSTALLATION
For Linux and Windows: The MySQLi extension is automatically installed in most cases, when php5 mysql package is installed.
PDO INSTALLATION
OPEN A CONNECTION TO MYSQL
Before we can access data in the MySQL database, we need to be able to connect to the server:
Example (MySQLi Object-Oriented)
<?php
$servername = "localhost";
$username = "username";
$password = "password";
// Create connection
$conn = new mysqli($servername, $username, $password);
// Check connection
if ($conn->connect_error) {
die("Connection failed: " . $conn->connect_error);
}
echo "Connected successfully";
?>
 | Note on the object-oriented example above: $connect_error was broken until PHP 5.2.9 and 5.3.0. If you need to ensure compatibility with PHP versions prior to 5.2.9 and 5.3.0, use the following code instead:
// Check connection
if (mysqli_connect_error()) {
die("Database connection failed: " . mysqli_connect_error());
} |
|---|
Example (MySQLi Procedural)
<?php
$servername = "localhost";
$username = "username";
$password = "password";
// Create connection
$conn = mysqli_connect($servername, $username, $password);
// Check connection
if (!$conn) {
die("Connection failed: " . mysqli_connect_error());
}
echo "Connected successfully";
?>
Example (PDO)
<?php
$servername = "localhost";
$username = "username";
$password = "password";
try {
$conn = new PDO("mysql:host=$servername;dbname=myDB", $username, $password);
// set the PDO error mode to exception
$conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
echo "Connected successfully";
}
catch(PDOException $e)
{
echo "Connection failed: " . $e->getMessage();
}
?>
| Notice that in the PDO example above we have also specified a database (myDB).
PDO require a valid database to connect to. If no database is specified,
an exception is thrown.
|
|---|
Tip: A great benefit of PDO is that it has an exception class to handle any problems that may occur in our database queries. If an exception is thrown within the try{ } block, the script stops executing and flows directly to the first catch(){ } block.
CLOSE THE CONNECTION
The connection will be closed automatically when the script ends. To close the connection before, use the following:
Example (MySQLi Object-Oriented)
$conn->close();
Example (MySQLi Procedural)
mysqli_close($conn);
Example (PDO)
$conn = null;
