PDO Learning Notes

The PDO extension defines a lightweight, consistent interface for the PHP Access database, which provides a data access abstraction layer so that queries and data can be executed through a consistent function, regardless of the database used.
PDO is released with PHP5.1 and can be used in the PHP5.0 pecl extension and cannot be run in previous versions of PHP.

In the presence of PDO, the functions that connect to the database in PHP vary depending on the database.
For example, MySQL uses the Mysql_connect function, the PostgreSQL database with the Pg_connect function.

The code written by PDO, the database changes in the future, only need to properly modify the database connection parameters, no need to modify the logic code.

The drivers for PDO and the main database are released as extensions with PHP, and to activate them simply edit the php.ini file:
extension=php_pdo.dll
Then, select the DLL files for the specific database using the DL () to load at run time, or enable them after php_pdo.dll the lines in the php.ini file, such as:

extension=php_pdo.dllextension=php_pdo_mysql.dllextension=php_pdo_pgsql.dllextension=php_pdo_sqlite.dll

MySQL database connection

$dsn'mysql:dbname=yii2test;host=localhost';$user'sqluser';$password'sqlpassword';$dbnew PDO($dsn$user$password);try{    $dbhnew PDO($dsn$user$password);}catch$e){    print('Error:'.$e->getMessage());    die();}

PostgreSQL database Connection

$dsn'pgsql:dbname=yii2test host=localhost port=5432';$user'sqluser';$password'sqlpassword';try{    $dbhnew PDO($dsn$user$password);}catch$e){    print('Error:'.$e->getMessage());    die();}

SQLite database Connection

$dsn'sqlite:d:/sqlite/yii2test.db';$user'';$password'';try{    $dbhnew PDO($dsn$user$password);}catch$e){    print('Error:'.$e->getMessage());    die();}

PDO operation MySQL Database demo code:

    $dsn=' mysql:dbname=yii2test;host=192.168.0.69;post=3306 ';$user=' Shou ';$password=' Shouadmin ';Try{$db=NewPDO ($dsn,$user,$password);// $sql=' INSERT into user (username, password,password_hash, status) value (?,?,?,?) ';$stmt=$db->prepare ($sql);$param= [];$param[] =' admin '. Date' Ymdhis ');$param[] = time ();$param[] = MD5 (time ());$param[] =Ten;if($stmt->execute ($param)) {Echo"Insert ok!".    Php_eol; }Else{Echo"Insert ng!".    Php_eol; }// EchoPhp_eol."==> Query". Php_eol;$sql="SELECT * from User";$data=$db->query ($sql);foreach($data as$row) {Echo$row["username"] ."  ".$row["Password"].    Php_eol; }// EchoPhp_eol."==> prepare 1". Php_eol;$sql=' SELECT * from user where username? ';$stmt=$db->prepare ($sql);$stmt->execute ([' admin% ']); while($result=$stmt->fetch (PDO::FETCH_ASSOC)) {Print_r ($result); }// EchoPhp_eol."==> prepare 2". Php_eol;$sql=' SELECT * from user where username Like:username ';$stmt=$db->prepare ($sql);$stmt->execute ([': Username '=' admin% ']); while($result=$stmt->fetch (PDO::FETCH_ASSOC)) {Print_r ($result); }}Catch(pdoexception$e){Print(' Error: '.$e->getmessage ()); die();}//Close database connection$db=NULL;

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