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This article mainly explains how PHP uses PDO to connect to the database. Interested friends may wish to have a look at it. The method introduced in this paper is simple, fast and practical. Let's let the editor take you to learn how PHP uses PDO to connect to the database.

What is PDO?

PDO is the abbreviation of PHP data object. To be exact, PDO is an interface defined by PHP to access the database. It provides the same function to execute queries and obtain data. This interface is lightweight and consistent, and no matter what database you use, it can be accessed and executed through the same function. This operation greatly simplifies the operation of the database, and we do not have to make changes according to the differences of the database.

In this way, with PDO, you no longer have to use a series of functions of mysqli_*, you only need to use the methods in PDO to manipulate the database.

We can think of PDO as a "database access abstraction layer", which is used to unify the access interface of various databases. PDO will unify the common features of different databases through a lightweight, clear and convenient function to achieve maximum abstraction and compatibility of PHP scripts.

The PDO extension is modular and can load drivers for the back end of the user database at run time without having to recompile or reinstall the entire PHP program.

How to turn on PDO

By default, PDO is turned on in PHP, but some drivers for a database still need to be opened if they want to start it.

Let's take windows as an example to find the relevant configuration information of PDO in the php.ini configuration file:

In order to open the corresponding configuration, you only need to remove the semicolon before the configuration item; and then restart the Apache server.

After the configuration is completed, you can use phpinfo () to check whether it is enabled successfully. The example is as follows:

The following results can be found in the output:

So we open PDO through the php.ini configuration file, now that we have enabled pdo, here is how to connect to the database, then let's take a look at how to use PDO to connect to the database in PHP.

PHP uses PDO to connect to the database

PHP wants to use PDO to connect to the database is to interact with different databases, when the member methods in the PDO object agree to the access interface of various databases, in order to achieve the purpose of interacting with different databases. So before using PDO to interact with the database, we first create a PDO object, and then connect to the database through the object's constructor. The syntax format of this constructor is as follows:

PDO::__construct (string $dsn [, string $username [, string $password [, array $driver_options])

Among them, it should be noted that:

Dsn represents the name of the data source, or DSN, and contains information about the request to connect to the database. Usually a DSN consists of the name of the PDO driver, followed by a colon, followed by the database connection information of the optional driver.

$username represents an optional parameter and is used to represent the user name in the DSN string

$password represents an optional parameter and is used to represent the password in the DSN string

Driver_options represents an optional parameter, a key / value array of connection options for a specific driver.

You can call the constructor to create a PDO object in a variety of ways. Take connecting to the MySQL database as an example to introduce a variety of ways to call the constructor.

Examples are as follows:

In the above example, the parameters are embedded in the constructor, the mysql driver is loaded in the DSN string, and two optional parameters are specified: the first is the database name, and the second is the database address. Other drivers will also interpret its DSN in different ways, and if the driver cannot be loaded, or if a connection failure occurs, a PDOException will be thrown so that you can decide how best to handle the failure.

The parameters can also be stored in a local or remote file and then referenced in the constructor, as shown in the following example:

First, create a dsn.txt file in the local file, with the content and path as follows:

Then enter an example as follows:

So we store the erase book in the file through the bar, and then complete the call to the database through the constructor.

At this point, I believe you have a deeper understanding of "how PHP uses PDO to connect to the database". You might as well do it in practice. Here is the website, more related content can enter the relevant channels to inquire, follow us, continue to learn!

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