PHP 7.0.6 Released

    Overview

    This section provides an introduction to the options available to you when developing a PHP application that needs to interact with a MySQL database.

    What is an API?

    An Application Programming Interface, or API, defines the classes, methods, functions and variables that your application will need to call in order to carry out its desired task. In the case of PHP applications that need to communicate with databases the necessary APIs are usually exposed via PHP extensions.

    APIs can be procedural or object-oriented. With a procedural API you call functions to carry out tasks, with the object-oriented API you instantiate classes and then call methods on the resulting objects. Of the two the latter is usually the preferred interface, as it is more modern and leads to better organized code.

    When writing PHP applications that need to connect to the MySQL server there are several API options available. This document discusses what is available and how to select the best solution for your application.

    What is a Connector?

    In the MySQL documentation, the term connector refers to a piece of software that allows your application to connect to the MySQL database server. MySQL provides connectors for a variety of languages, including PHP.

    If your PHP application needs to communicate with a database server you will need to write PHP code to perform such activities as connecting to the database server, querying the database and other database-related functions. Software is required to provide the API that your PHP application will use, and also handle the communication between your application and the database server, possibly using other intermediate libraries where necessary. This software is known generically as a connector, as it allows your application to connect to a database server.

    What is a Driver?

    A driver is a piece of software designed to communicate with a specific type of database server. The driver may also call a library, such as the MySQL Client Library or the MySQL Native Driver. These libraries implement the low-level protocol used to communicate with the MySQL database server.

    By way of an example, the PHP Data Objects (PDO) database abstraction layer may use one of several database-specific drivers. One of the drivers it has available is the PDO MYSQL driver, which allows it to interface with the MySQL server.

    Sometimes people use the terms connector and driver interchangeably, this can be confusing. In the MySQL-related documentation the term "driver" is reserved for software that provides the database-specific part of a connector package.

    What is an Extension?

    In the PHP documentation you will come across another term - extension. The PHP code consists of a core, with optional extensions to the core functionality. PHP's MySQL-related extensions, such as the mysqli extension, and the mysql extension, are implemented using the PHP extension framework.

    An extension typically exposes an API to the PHP programmer, to allow its facilities to be used programmatically. However, some extensions which use the PHP extension framework do not expose an API to the PHP programmer.

    The PDO MySQL driver extension, for example, does not expose an API to the PHP programmer, but provides an interface to the PDO layer above it.

    The terms API and extension should not be taken to mean the same thing, as an extension may not necessarily expose an API to the programmer.

    What are the main PHP API offerings for using MySQL?

    There are three main API options when considering connecting to a MySQL database server:

    • PHP's MySQL Extension

    • PHP's mysqli Extension

    • PHP Data Objects (PDO)

    Each has its own advantages and disadvantages. The following discussion aims to give a brief introduction to the key aspects of each API.

    What is PHP's MySQL Extension?

    This is the original extension designed to allow you to develop PHP applications that interact with a MySQL database. The mysql extension provides a procedural interface and is intended for use only with MySQL versions older than 4.1.3. This extension can be used with versions of MySQL 4.1.3 or newer, but not all of the latest MySQL server features will be available.

    Note:

    If you are using MySQL versions 4.1.3 or later it is strongly recommended that you use the mysqli extension instead.

    The mysql extension source code is located in the PHP extension directory ext/mysql.

    For further information on the mysql extension, see MySQL (Original).

    What is PHP's mysqli Extension?

    The mysqli extension, or as it is sometimes known, the MySQL improved extension, was developed to take advantage of new features found in MySQL systems versions 4.1.3 and newer. The mysqli extension is included with PHP versions 5 and later.

    The mysqli extension has a number of benefits, the key enhancements over the mysql extension being:

    • Object-oriented interface

    • Support for Prepared Statements

    • Support for Multiple Statements

    • Support for Transactions

    • Enhanced debugging capabilities

    • Embedded server support

    Note:

    If you are using MySQL versions 4.1.3 or later it is strongly recommended that you use this extension.

    As well as the object-oriented interface the extension also provides a procedural interface.

    The mysqli extension is built using the PHP extension framework, its source code is located in the directory ext/mysqli.

    For further information on the mysqli extension, see MySQLi.

    What is PDO?

    PHP Data Objects, or PDO, is a database abstraction layer specifically for PHP applications. PDO provides a consistent API for your PHP application regardless of the type of database server your application will connect to. In theory, if you are using the PDO API, you could switch the database server you used, from say Firebird to MySQL, and only need to make minor changes to your PHP code.

    Other examples of database abstraction layers include JDBC for Java applications and DBI for Perl.

    While PDO has its advantages, such as a clean, simple, portable API, its main disadvantage is that it doesn't allow you to use all of the advanced features that are available in the latest versions of MySQL server. For example, PDO does not allow you to use MySQL's support for Multiple Statements.

    PDO is implemented using the PHP extension framework, its source code is located in the directory ext/pdo.

    For further information on PDO, see the PDO.

    What is the PDO MYSQL driver?

    The PDO MYSQL driver is not an API as such, at least from the PHP programmer's perspective. In fact the PDO MYSQL driver sits in the layer below PDO itself and provides MySQL-specific functionality. The programmer still calls the PDO API, but PDO uses the PDO MYSQL driver to carry out communication with the MySQL server.

    The PDO MYSQL driver is one of several available PDO drivers. Other PDO drivers available include those for the Firebird and PostgreSQL database servers.

    The PDO MYSQL driver is implemented using the PHP extension framework. Its source code is located in the directory ext/pdo_mysql. It does not expose an API to the PHP programmer.

    For further information on the PDO MYSQL driver, see MySQL (PDO).

    What is PHP's MySQL Native Driver?

    In order to communicate with the MySQL database server the mysql extension, mysqli and the PDO MYSQL driver each use a low-level library that implements the required protocol. In the past, the only available library was the MySQL Client Library, otherwise known as libmysqlclient.

    However, the interface presented by libmysqlclient was not optimized for communication with PHP applications, as libmysqlclient was originally designed with C applications in mind. For this reason the MySQL Native Driver, mysqlnd, was developed as an alternative to libmysqlclient for PHP applications.

    The mysql extension, the mysqli extension and the PDO MySQL driver can each be individually configured to use either libmysqlclient or mysqlnd. As mysqlnd is designed specifically to be utilised in the PHP system it has numerous memory and speed enhancements over libmysqlclient. You are strongly encouraged to take advantage of these improvements.

    Note:

    The MySQL Native Driver can only be used with MySQL server versions 4.1.3 and later.

    The MySQL Native Driver is implemented using the PHP extension framework. The source code is located in ext/mysqlnd. It does not expose an API to the PHP programmer.

    Comparison of Features

    The following table compares the functionality of the three main methods of connecting to MySQL from PHP:

    Comparison of MySQL API options for PHP
      PHP's mysqli Extension PDO (Using PDO MySQL Driver and MySQL Native Driver) PHP's MySQL Extension
    PHP version introduced 5.0 5.0 Prior to 3.0
    Included with PHP 5.x yes yes Yes
    MySQL development status Active development Active development as of PHP 5.3 Maintenance only
    Recommended by MySQL for new projects Yes - preferred option Yes No
    API supports Charsets Yes Yes No
    API supports server-side Prepared Statements Yes Yes No
    API supports client-side Prepared Statements No Yes No
    API supports Stored Procedures Yes Yes No
    API supports Multiple Statements Yes Most No
    Supports all MySQL 4.1+ functionality Yes Most No

    User Contributed Notes

    php-includer at gmail dot com
    1 year ago
    mysqli can be great in some circumstances but much work has been put into PHP Portable Data Objects (PDO) which you should also consider when choosing a way to connect to your database using php. For example, PDO supports MySQL with minimal performance hit and the code your write for it will support many other databases with little or no changes. That said, the database connection code, even if you have to change a lot of it to use another database will be much less work than coding your actual database data entry and report apps. When I started creating PHP/MySQL apps years ago, I used php's native support for PHP then moved to PEAR:DB and MDB/MDB2 and finally to wizzyweb which is basically like "phpMyAdmin for Apps" to create apps as it automatically generates the PHP PDO connection code and the application code. Sure, I could code it all from scratch but I save about 90% of the time it used to take. The point is look at the total amount of time you will save by using native code vs. an abstraction layer. Most people find that programmer time is the most valuable part of the equation so anything than can save programmer time should be heavily weighted.
    guatebus at dot gmail dot com
    2 years ago
    The text: "PDO does not allow you to use MySQL's support for Multiple Statements" is outdated.

    Since v5.3, PHP intoduced multiple statement support into PDO (by PDO_MYSQLND driver replacing the previous PDO_MYSQL).
    AvenidaGez
    1 year ago
    Even when not usually written, a Driver is a Device Driver. Something physical, hardware, needs a Driver, and in computer terms is the code or program needed by the device to work properly.
    An API (Application program interface), is the part of exposed code of a program so you can communicate with it, you could say is like the buttons of a blender, the steering wheel of a car, if there is no interface there is no way to communicate.
    MySQL is software, not hardware, not a device, so it is a Driver in itself that makes a computer work as a database (an specific Application), so MySQL has an API too, but it does not need nor uses a Driver since it is the Driver.
    Sometimes you have a Driver, with its API, but you can not communicate with it, with what you have, so the language needs to be extended, in this case, the capabilities of the language you are using, in order for it to be able to communicate with the API of the Driver (in this case MySQL Driver), so that is called and Extension (of the language you are using), and it is not and API, neither a Driver, is just that, and Extension. Then why it is called API (application program interface) and not DPI (device program interface), well, that is because a Device might have different Applications, (read it as different uses) for example an USB device, might be used as storage device, as audio CD, as DVD movie, etc. so the interface is oriented to the application of the device and not to the device itself.
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