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This article introduces the relevant knowledge of "what is PHP PDO". In the operation of actual cases, many people will encounter such a dilemma. Then let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

1. The PDO (PHP Data Object) extension defines a lightweight, persistent interface for PHP to access the database. Each database driver that implements the PDO interface can show its own characteristics in the form of regular extension.

Main: PDO extension is only an abstract interface layer. Using PDO extension itself can not realize any database operation. You must use a specific database PDO driver to access the database.

2. Start the PDO method: find the php.ini file and

The copy code is as follows:

; extension=php_pdo.dll

Just remove the front semicolon (similar in linux environment)

3. PDO predefined classes:

PDO contains three predefined classes: PDO, PDOStatement, and PDOException

(1) PDO class: represents a connection between a PHP and a database

PDO: constructor to create a new PDO object

BeginTransaction: start a transaction

Commit: commit transaction

ErrorCode: returns an error code from the database, if any

ErrorInfo: returns an array of error messages from the database, if any

Exec: executes a SQL statement and returns the number of rows affected

GetAttribute: returns the connection properties of a database

LastInsertId: returns the latest row inserted into the database (ID)

Prepare: prepares a SQL statement for execution and returns the federated result set after the statement is executed

Query: executes a SQL statement and returns the result set

RollBack: rolls back a transaction

SetAttribute: set a database connection property

(2) PDOStatement class: represents a preprocessing statement and the federated result set after the statement is executed

BindColomn: bind a PHP variable to the output column of the result set

BindParam: bind a variable to a parameter in a PHP preprocessing statement

BindValue: bind a value to a parameter in a processing statement

CloseCursor: close the cursor so that the statement can be executed again

CloumnCount: returns the number of columns in the result set

ErrorCode: returns an error code from the statement, if any

ErrorInfo: returns an array containing error messages from a statement

Execute: execute a preprocessing statement

Fetch: fetches a row from the result set

FetchAll: fetches an array containing all rows from the result set

FetchColomn: returns the data of a column in the result set

GetAttribute: returns a PDOStatement property

GetColomnMeta: returns the structure of a column in the result set

NextRowset: returns the next result set

RowCount: returns the number of rows affected after the execution of the SQL statement

SetAttribute: set a PDOStatement property

SetFetchMode: setting for PDOStatement to get data

Give a simple example of transaction processing:

The copy code is as follows:

(main features of transactions: atomicity, consistency, independence, and persistence)

4. The most important feature of PDO is the introduction of parameter binding and precompilation.

Precompilation is responsible for two things, transfer and soft parsing speed up. To support precompilation, driver support (PDO and NySQLi support) is required in addition to database support.

5. The efficiency of PDO

(1) when tested in a large table and a large amount of data, the CRUD efficiency of PDO is 5% and 15% lower than that of MySql direct connection, and the variance is greater than that of MySQL direct connection.

(2) as for the load, the load of PDO is higher than that of MySQL and is relatively stable after opening the persistent connection.

This is the end of "what is PHP PDO". Thank you for your reading. If you want to know more about the industry, you can follow the website, the editor will output more high-quality practical articles for you!

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