PHPPDO

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, but cannot run on previous PHP versions.

PDO installation

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

Install PDO on Unix systems

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

 extension=pdo.so

Windows users

PDO and all major drivers are shipped with PHP as shared extensions. To activate them simply edit the php.ini file and add the following extension:

 extension=php_pdo.dll

 ;extension=php_pdo_firebird.dll;extension=php_pdo_informix.dll;extension=php_pdo_mssql.dll;extension=php_pdo_mysql.dll;extensio n=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='mysql'; //Database type $host='localhost'; //Database host name $dbName='test'; //Database used $user='root'; //Database connection user Name $pass=''; //Corresponding password $dsn="$dbms:host=$host;dbname=$dbName"; try { $dbh = new PDO($dsn, $user, $pass); //Initialize a PDO object echo "Connection successful<br/>"; /*You can also perform a search operation foreach ($dbh->query('SELECT * from FOO') as $row) { print_r($row) ; //You can use echo($GLOBAL); to see these values} */ $dbh = null;} catch (PDOException $e) { die ("Error!: " . $e->getMessage() . "<br/>");}//By default, this is not a long connection. If you need a long connection to the database, you need to add a parameter at the end: array(PDO::ATTR_PERSISTENT => true) It becomes like this: $db = new PDO( $dsn, $user, $pass, array(PDO::ATTR_PERSISTENT => true));?>

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

Predefined 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 that represents a database connection

PDO::errorCode — Get the SQLSTATE associated with the last operation of the database handle

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

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

PDO::getAttribute — Retrieve attributes of a database connection

PDO::getAvailableDrivers — Returns an array of available drivers

PDO::inTransaction — Check if within a transaction

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

PDO::prepare — Prepares a SQL statement to be executed and returns a PDOStatement object

PDO::query — Execute SQL statements and return PDOStatement objects, which can be understood as result sets

PDO::quote — Add quotes to strings in SQL statements.

PDO::rollBack — roll back a transaction

PDO::setAttribute — set an attribute

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 — Closes the cursor so that the statement can be executed again.

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

PDOStatement::debugDumpParams — Print a SQL preprocessing command

PDOStatement::errorCode — Get the SQLSTATE associated with 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 — Returns an array containing all rows in the result set

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

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

PDOStatement::getAttribute — Retrieve a statement attribute

PDOStatement::getColumnMeta — Returns 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 — Set a statement attribute

PDOStatement::setFetchMode — Set the default fetch mode for statements.