[php tutorial] PHP PDO

PHP PDO

The PHP Data Objects (PDO) extension defines a lightweight, consistent interface for PHP to access databases.

PDO provides a data access abstraction layer, which means that no matter which database is used, the same functions (methods) can be used to query and obtain data.

PDO is released with PHP5.1 and can also be used in the PECL extension of PHP5.0. It cannot run on previous PHP versions.

PDO installation

You can check whether the PDO extension is installed through PHP's phpinfo() function.

Installing PDO on Unix systems

On Unix or Linux you need to add the following extensions:

extension=pdo.so

Windows users

PDO and all major drivers are distributed with PHP as shared extensions, to activate them simply Edit the php.ini file and add the following extensions:

extension=php_pdo.dll

In addition, there are various database extensions corresponding to the following:

;extension=php_pdo_firebird.dll
;extension=php_pdo_informix.dll
;extension=php_pdo_mssql.dll
;extension=php_pdo_mysql.dll
;extension=php_pdo_oci.dll
;extension=php_pdo_oci8.dll
;extension=php_pdo_odbc.dll
;extension=php_pdo_pgsql.dll
;extension=php_pdo_sqlite.dll

After setting these configurations, we need to restart PHP or the Web server.

Next let’s take a look at specific examples. The following is an example of using PDO to connect to a MySql database:

<?php
$dbms=&#39;mysql&#39;;     //数据库类型
$host=&#39;localhost&#39;; //数据库主机名
$dbName=&#39;test&#39;;    //使用的数据库
$user=&#39;root&#39;;      //数据库连接用户名
$pass=&#39;&#39;;          //对应的密码
$dsn="$dbms:host=$host;dbname=$dbName";


try {
    $dbh = new PDO($dsn, $user, $pass); //初始化一个PDO对象
    echo "连接成功<br/>";
    /*你还可以进行一次搜索操作
    foreach ($dbh->query(&#39;SELECT * from FOO&#39;) as $row) {
        print_r($row); //你可以用 echo($GLOBAL); 来看到这些值
    }
    */
    $dbh = null;
} catch (PDOException $e) {
    die ("Error!: " . $e->getMessage() . "<br/>");
}
//默认这个不是长连接，如果需要数据库长连接，需要最后加一个参数：array(PDO::ATTR_PERSISTENT => true) 变成这样：
$db = new PDO($dsn, $user, $pass, array(PDO::ATTR_PERSISTENT => true));

?>

It’s very simple. Next, let’s take a look at the specific instructions of PHP PDO:

Preliminary Define constants

PHP PDO connection connection management

PHP PDO transactions and automatic commit

PHP PDO prepared statements and stored procedures

PHP PDO errors and error handling

PHP PDO large objects (LOBs)

PDO class:

PDO::beginTransaction — Start a transaction

PDO::commit — Commit a transaction

PDO::__construct — Create a PDO instance representing a database connection

PDO::errorCode — Get the database handle SQLSTATE related to an operation

PDO::errorInfo — Returns the error message of the last database operation

PDO::exec — Execute an SQL statement and return the number of affected rows

PDO::getAttribute — Retrieve a database Connection properties

PDO::getAvailableDrivers — Returns an array of available drivers

PDO::inTransaction — Checks if within a transaction

PDO::lastInsertId — Returns the ID or sequence value of the last inserted row

PDO:: prepare — Prepare the SQL statement to be executed and return a PDOStatement object

PDO::query — Execute the SQL statement and return the PDOStatement object, which can be understood as a result set

PDO::quote — Add quotation marks to the string in the SQL statement.

PDO::rollBack — Roll back a transaction

PDO::setAttribute — Set attributes

PDOStatement class:

PDOStatement::bindColumn — Bind a column to a PHP variable

PDOStatement::bindParam — Bind a Parameter to the specified variable name

PDOStatement::bindValue — Bind a value to a parameter

PDOStatement::closeCursor — Close the cursor so that the statement can be executed again.

PDOStatement::columnCount — Return the number of columns in the result set

PDOStatement::debugDumpParams — Print a SQL preprocessing command

PDOStatement::errorCode — Get the SQLSTATE related to the last statement handle operation

PDOStatement::errorInfo — Get extended error information related to the last statement handle operation

PDOStatement::execute — Execute a prepared statement

PDOStatement::fetch — Get the next row from the result set

PDOStatement::fetchAll — Return a list containing all the results in the result set Array of rows

PDOStatement::fetchColumn — Returns a single column from the next row in the result set.

PDOStatement::fetchObject — Gets the next line and returns it as an object.

PDOStatement::getAttribute — Retrieve a statement attribute

PDOStatement::getColumnMeta — Return metadata for a column in a result set

PDOStatement::nextRowset — Advance to the next rowset in a multi-rowset statement handle

PDOStatement: :rowCount — Returns the number of rows affected by the previous SQL statement

PDOStatement::setAttribute — Sets a statement attribute

PDOStatement::setFetchMode — Sets the default fetch mode for the statement.

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