Tips on using PHP database connection function library

With the continuous development of Internet technology, PHP, as an important server-side scripting language, has been widely used. In WEB application development, the use of databases is very common. Connecting to the database is the first step in PHP development. Here are some tips for using the PHP database connection function library.

1. MYSQLI extension library

The MYSQLI extension library is only available after the PHP5 version. It is more optimized and stable than the previous MYSQL extension library. The MYSQLI extension library provides a more powerful and convenient function library. When using it, you need to create a database connection object first, and then use the object to perform related operations.

1. Create a connection object

You need to use the mysqli_connect() function to connect to the MYSQLI extension library. The syntax is as follows:

mysqli_connect(host, username, password, dbname, port, socket);

Parameter description:

host: The host address where the database is located, the default is localhost.

username: database username.

password: database password.

dbname: The name of the database to be connected.

port: Port number of the database service, default 3306.

socket: The data source address of the MySQL server, the default is the built-in value.

2. Execute query statements

You need to use the mysqli_query() function to execute query statements. Its syntax is as follows:

mysqli_query(connection,query);

Parameter description:

connection: database connection object.

query: SQL query statement that needs to be executed.

3. Processing the result set

To process the result set returned by the query statement, you need to use the mysqli_fetch_array() function, whose syntax is as follows:

mysqli_fetch_array(result,resulttype );

Parameter description:

result: The result set returned by the query statement.

resulttype: Optional parameter, indicating the return array type: MYSQLI_ASSOC-associative array, MYSQLI_NUM-numeric array, MYSQLI_BOTH-returns both associative array and numeric array. Default is MYSQLI_BOTH.

2. PDO extension library

PDO extension library is the PDO class library after PHP5 version. It provides a unified interface and supports multiple database types: MySQL, Oracle, SqlServer, etc. , and supports functions such as transactions and prepared statements.

1. Create a connection object

To connect to the PDO database, you need to use the PDO constructor. Its syntax is as follows:

new PDO(dsn, username,password, options);

Parameter description:

dsn: data source name, the format is: driver:host=hostname;dbname=dbname, driver represents the database type, hostname represents the host address of the database, dbname Represents the database name.

username: database username.

password: database password.

options: Optional parameters, indicating PDO options, such as: PDO::ATTR_ERRMODE-error reporting mode, PDO::ATTR_DEFAULT_FETCH_MODE-default extraction mode, PDO::ATTR_EMULATE_PREPARES-use prepared statements, etc. Defaults to array().

2. Execute query statements

To execute query statements, you need to use the query() method of the PDO class. The syntax is as follows:

query(sql);

Parameter description:

sql: SQL query statement to be executed.

3. Processing result sets

The PDO class provides a variety of methods to process result sets, such as fetch(), fetchAll(), fetchColumn(), etc. Here we use fetch () method as an example, its syntax is as follows:

fetch(fetch_style);

Parameter description:

fetch_style: result set return type, which can be PDO::FETCH_NUM- Numeric array, PDO::FETCH_ASSOC - associative array, PDO::FETCH_BOTH - returns both associative array and numeric array, etc.

3. Example demonstration

The following takes the MYSQLI extension library as an example to demonstrate how to connect to the database and execute query statements.

$host = 'localhost';
$username = 'root';
$password = 'root';
$dbname = 'test';

//Create connection object
$conn = mysqli_connect($host, $username, $password, $dbname);
if(mysqli_connect_errno()){

die('连接失败，错误信息：'.mysqli_connect_error());

}

//Execute the query statement
$sql = 'select * from user';
$result = mysqli_query($conn, $sql);

//Process the query results
while($row = mysqli_fetch_array($result)){

print_r($row);

}

//Close the database connection
mysqli_close($conn);
?>

The above code connects to the test database, queries the data of the user table, and prints the results.

4. Summary

The above is an introduction to the usage skills of the PHP database connection function library. By connecting the MYSQLI extension library and the PDO extension library, we can easily perform related operations and improve WEB application development. efficiency and quality. In actual development, it is necessary to flexibly use different function libraries and select the most suitable method for connection and operation.

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