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이 문서에서는 PHP 중국어 웹사이트 매뉴얼 풀어 주다
(PHP 5 >= 5.1.0, PECL pdo >= 0.1.0)
PDO::__construct — 创建一个表示数据库连接的 PDO 实例
$dsn
[, string $username
[, string $password
[, array $driver_options
]]] )创建一个表示连接到请求数据库的数据库连接 PDO 实例。
数据源名称或叫做 DSN,包含了请求连接到数据库的信息。
通常,一个 DSN 由 PDO 驱动名、紧随其后的冒号、以及具体 PDO 驱动的连接语法组成。更深入的信息能从 PDO 具体驱动文档找到。
The dsn
参数支持三种不同的方式 创建一个数据库连接:
dsn
包含完整的DSN。
dsn
consists of uri:
followed by a URI that defines the location of a file containing
the DSN string. The URI can specify a local file or a remote URL.
uri:file:///path/to/dsnfile
dsn
consists of a name
name
that maps to
pdo.dsn.
in php.ini
defining the DSN string.
name
Note:
别名必须得在 php.ini 中定义了,不能是在 .htaccess 或 httpd.conf 中 。
DSN字符串中的用户名。对于某些PDO驱动,此参数为可选项。
DSN字符串中的密码。对于某些PDO驱动,此参数为可选项。
一个具体驱动的连接选项的键=>值数组。
成功则返回一个PDO对象。
如果试图连接到请求的数据库失败,则 PDO::__construct() 抛出一个 PDO异常(PDOException) 。
Example #1 Create a PDO instance via driver invocation
<?php
$dsn = 'mysql:dbname=testdb;host=127.0.0.1' ;
$user = 'dbuser' ;
$password = 'dbpass' ;
try {
$dbh = new PDO ( $dsn , $user , $password );
} catch ( PDOException $e ) {
echo 'Connection failed: ' . $e -> getMessage ();
}
?>
Example #2 Create a PDO instance via URI invocation
The following example assumes that the file /usr/local/dbconnect exists with file permissions that enable PHP to read the file. The file contains the PDO DSN to connect to a DB2 database through the PDO_ODBC driver:
odbc:DSN=SAMPLE;UID=john;PWD=mypass
The PHP script can then create a database connection by simply passing the uri: parameter and pointing to the file URI:
<?php
$dsn = 'uri:file:///usr/local/dbconnect' ;
$user = '' ;
$password = '' ;
try {
$dbh = new PDO ( $dsn , $user , $password );
} catch ( PDOException $e ) {
echo 'Connection failed: ' . $e -> getMessage ();
}
?>
Example #3 使用别名创建一个PDO实例
The following example assumes that php.ini contains the following entry to enable a connection to a MySQL database using only the alias mydb:
[PDO] pdo.dsn.mydb="mysql:dbname=testdb;host=localhost"
<?php
$dsn = 'mydb' ;
$user = '' ;
$password = '' ;
try {
$dbh = new PDO ( $dsn , $user , $password );
} catch ( PDOException $e ) {
echo 'Connection failed: ' . $e -> getMessage ();
}
?>
[#1] ohcc at 163 dot com [2015-11-24 19:03:32]
<?php
// PDO::__construct can end up with a fatal error rather than throw an exception even if you try ... catch ... .
try{
$db = new PDO(
// a database to which connection may fail
'mysql:host=www.wuxiancheng.cn; dbname=php; port=3306; charset=utf8',
'root',
'rx00t',
array(
PDO::ATTR_ERRMODE=>PDO::ERRMODE_EXCEPTION,
PDO::ATTR_TIMEOUT=>1,
)
);
}catch(PDOException $pe){
// test the following lines of code respectively, and you will find the first line and the second line will end up with a fatal error.
throw $pe; // Fatal error: in path\file.php on line n, script ends, no exception thrown
throw new PDOException($pe->getMessage()); //Fatal error: in path\file.php on line n, script ends, no exception thrown
throw new PDOException ('cannot connect to the database'); // an exception is thrown as expected
throw new PDOException('error: '.$pe->getMessage()); //Fatal error: in path\file.php on line n, script ends, no exception thrown
throw new PDOException($pe->getLine()); // an exception is thrown as expected
throw new PDOException($pe->getFile()); // an exception is thrown as expected
throw new PDOException($pe->getCode()); // an exception is thrown as expected
throw new PDOException($pe->getTraceAsString()); // an exception is thrown as expected
}
?>
[#2] ohcc at 163 dot com [2015-11-23 05:37:57]
You will get a fatal error if you don't catch the exception threw by PDO when it fails to connect to the database server like this.
Fatal error: in xxx.php on line xx
This error neither can be handled by error handlers nor can it be erased by the @ sign, which can make your script uncontrollable.
<?php
$db = new pdo('mysql:host=127.0.0.1;port=3306;dbname=mysql;charset=utf8','user','password',array(
PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
));
?>
You should always try ... catch ...
<?php
try{
$db = new pdo('mysql:host=127.0.0.1;port=3306;dbname=mysql;charset=utf8','user','password',array(
PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
));
}catch(PDOException $pe){
echo $pe->getMessage();
}
?>
[#3] daviddlavier at gmail dot com [2015-11-09 00:43:41]
I'd like to point out that in PHP 7.0 in the dsn parameter you can't use 'host=localhost' to solve this you can use 'host=127.0.0.1' instead.
[#4] info at salientdigital dot com [2015-04-18 03:24:37]
If you happen to create a dsn like this...
<?php
//wrong dsn
$db = new PDO('mysql:database=yourdb;host=127.0.0.1', 'user', 'password');
$stmt = $db->prepare('SELECT * FROM tbl WHERE id = :id');
$stmt->bindParam(':id', $user_id, PDO::PARAM_INT);
$result = $stmt->execute();
?>
... your result will be bool(false) and your $db->errorInfo() will be "0000" which isn't very helpful.
You have to look to the $stmt->errorInfo() to see "No database selected" which is even more confusing until you realize that it's not 'database' but 'dbname' in your DSN! You would think the error about a bad DSN would be in the $db errorInfo but it is not, it's not until you try the $stmt that the error is generated.
<?php
//correct dsn
$db = new PDO('mysql:dbname=yourdb;host=127.0.0.1', 'user', 'password');
?>
I wasted a half hour on that one.
[#5] berk0081 at umn dot edu [2014-11-16 13:34:08]
Although not explicitly stated, parameters in the PDO $dsn string may be case-sensitive on some platforms or drivers.
<?php
// The dbname will not be parsed with incorrect casing:
$pdo = new PDO("mysql:host=hostname;DBName=database", "user", "password");
// The correct dbname is lowercase, as displayed in the manual:
$pdo = new PDO("mysql:host=hostname;dbname=database", "user", "password");
?>
[#6] Anonymous [2014-04-07 13:55:13]
To connect to the database via a function use this and call the getConnection function in the class constructor.
<?php
class Connection{
protected $db;
public function Connection(){
$conn = NULL;
try{
$conn = new PDO("mysql:host=localhost;dbname=dbname", "dbuser", "dbpass");
$conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
} catch(PDOException $e){
echo 'ERROR: ' . $e->getMessage();
}
$this->db = $conn;
}
public function getConnection(){
return $this->db;
}
}
?>
[#7] Kiipa at live dot com [2013-10-19 18:46:08]
To get UTF-8 charset you can specify that in the DSN.
$link = new PDO("mysql:host=localhost;dbname=DB;charset=UTF8");
[#8] Anonymous [2013-05-29 05:30:36]
Sqlite:
<?php
try{
$pdo = new PDO('sqlite:example.db');
}catch (PDOException $e){
die ('DB Error');
}
?>
If 'example.db' does not exist, no exception is thrown but the file 'example.db' is created.
[#9] piotrekkr at o2 dot pl [2010-09-15 00:19:33]
To connect throught unix socket you need to use
<?php
$dsn = 'mysql:dbname=testdb;unix_socket=/path/to/socket';
?>
You musn't specify host when using socket.
[#10] Victor T. [2010-02-20 09:34:41]
If you use the UTF-8 encoding, you have to use the fourth parameter :
<?php
$db = new PDO('mysql:host=myhost;dbname=mydb', 'login', 'password', array(PDO::MYSQL_ATTR_INIT_COMMAND => 'SET NAMES \'UTF8\''));
?>
[#11] subme at interia dot pl [2008-11-25 14:03:45]
To specify a database connection port use the following DSN string
<?php
$dsn = 'mysql:dbname=testdb;host=127.0.0.1;port=3333';
?>