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pg_connect

(PHP 4, PHP 5, PHP 7, PHP 8)

pg_connect — 打开 PostgreSQL 连接

说明

pg_connect(string $connection_string, int $flags = 0): PgSql\Connection|false

pg_connect() 打开通过 connection_string 指定的 PostgreSQL 数据库的连接。

如果使用与现有连接相同的 connection_string 对 pg_connect() 进行第二次调用，将返回现有连接，除非将 PGSQL_CONNECT_FORCE_NEW 作为 flags 传递。

弃用有多个参数的旧语法 $conn = pg_connect("host", "port", "options", "tty", "dbname")。

参数

connection_string

connection_string 可以为空以使用所有默认参数，或者可以包含一个或多个由空格分隔的参数设置。每个参数设置的形式为 keyword = value。等号两旁的空格是可选的。写入空值或包含空格的值，请用单引号将其括起来，例如 keyword = 'a value'。值中的单引号和反斜线必须使用反斜线转义，即 \' 和 \\。

当前可识别的参数关键字有 host、hostaddr、port、dbname（默认为 user 的值）、user、password、connect_timeout、options、tty（忽略）、sslmode、requiressl（弃用 sslmode）和 service。存在哪些参数取决于 PostgreSQL 版本。

The options parameter can be used to set command line parameters to be invoked by the server.

flags

如果传递 PGSQL_CONNECT_FORCE_NEW，将会创建新连接，即使 connection_string 与现有连接相同。

如果指定 PGSQL_CONNECT_ASYNC，然后连接是异步创建。连接状态可以通过 pg_connect_poll() 或 pg_connection_status() 检测。

返回值

成功时返回 PgSql\Connection 实例，或者在失败时返回 false。

更新日志

版本	说明
8.1.0	现在返回 PgSql\Connection 实例；之前返回 resource。

示例

示例 #1 使用 pg_connect()

<?php
$dbconn = pg_connect("dbname=mary");
//connect to a database named "mary"

$dbconn2 = pg_connect("host=localhost port=5432 dbname=mary");
// connect to a database named "mary" on "localhost" at port "5432"

$dbconn3 = pg_connect("host=sheep port=5432 dbname=mary user=lamb password=foo");
//connect to a database named "mary" on the host "sheep" with a username and password

$conn_string = "host=sheep port=5432 dbname=test user=lamb password=bar";
$dbconn4 = pg_connect($conn_string);
//connect to a database named "test" on the host "sheep" with a username and password

$dbconn5 = pg_connect("host=localhost options='--client_encoding=UTF8'");
//connect to a database on "localhost" and set the command line parameter which tells the encoding is in UTF-8
?>

参见

pg_pconnect() - 打开一个持久的 PostgreSQL 连接
pg_close() - 关闭 PostgreSQL 连接
pg_host() - 返回和某连接关联的主机名
pg_port() - 返回 connection 相关的端口号
pg_tty() - 返回跟连接相关的 tty 名
pg_options() - 获得和 connection 相关的选项
pg_dbname() - 获取数据库名称

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User Contributed Notes 26 notes

down

lukasz dot wolczak at gmail dot com ¶

7 years ago

It is worth to know, that you can set application_name in connection string, consider this simple example:

<?php
$appName = $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI'];
$connStr = "host=localhost port=5432 dbname=postgres user=postgres options='--application_name=$appName'";

//simple check
$conn = pg_connect($connStr);
$result = pg_query($conn, "select * from pg_stat_activity");
var_dump(pg_fetch_all($result));

?>

By doing this move on cli or cgi you can see in pgAdmin what scripts are running or what requests are running on database. You can extend configuration of postgres to track slow queries and print application name to logs. It was very usuful to me to find out what and where should I optimize.

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Dave ¶

10 years ago

If you use pgbouncer and unix socket
and you pgbouncer.ini looks like this
listen_port = 6432
unix_socket_dir = /tmp

you connect like this

pg_connect('host=/tmp port=6432 dbname=DB user=USER password=PASS');

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Anonymous ¶

9 years ago

Getting md5 passwords was confusing because of a lack of documentation:

- set up your pg_hba.conf in order to use md5 password instead of 'trust' or 'ident'
- check if your postgres.conf has 'password_encryption=on' (depending on the version this might already be 'on').
- make sure to restart your postgres process.
- in PHP you just supply the username and password in _plain_ text:
'host=localhost port=5432 dbname=megadb user=megauser password=holyhandbagsbatmanthispasswordisinplaintext'
The postgres PHP library will automagically do the md5 encoding for you, no need to do it yourself.

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tim at buttersideup dot com ¶

15 years ago

It's not explicitly stated here, but you can also connect to PostgreSQL via a UNIX domain socket by leaving the host empty.  This should have less overhead than using TCP e.g.:

$dbh = new PDO('pgsql:user=exampleuser dbname=exampledb password=examplepass');

In fact as the C library call PQconnectdb underlies this implementation, you can supply anything that this library call would take - the "pgsql:" prefix gets stripped off before PQconnectdb is called, and if you supply any of the optional arguments (e.g. user), then these arguments will be added to the string that you supplied...  Check the docs for your relevant PostgreSQL client library: e.g.

http://www.postgresql.org/docs/8.3/static/libpq-connect.html

If you really want, you can use ';'s to separate your arguments - these will just be converted to spaces before PQconnectdb is called.

Tim.

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matias at nospam dot projectcast dot com ¶

21 years ago

At least with Postgres 7.2, connecting to local postgresdatabase requires a user in the database with the same name as the user running apache, or the connection fails.

down

thakur at corexprts dot com ¶

13 years ago

One thing is to remember, whenever trying to use pg_connect, add the timeout parameter with it



<?php

$d=pg_connect('host=example.com user=pgsql dbname=postgres connect_timeout=5');

?>

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bgalloway at citycarshare dot org ¶

15 years ago

Beware about writing something like 
<?php
function getdb_FAILS() {
    return pg_connect("...") or die('connection failed');
}
?>

It will return a boolean.  This will appear to be fine if you don't use the return value as a db connection handle, but will fail if you do.

Instead, use:
<?php
function getdb() {
    $db = pg_connect("...") or die('connection failed');
    return $db;
}
?>

which actually returns a handle.

down

VLroyrenn ¶

4 years ago

For what it's worth, it should be noted that, while PHP will generally handle connection-reuse for you so long as you keep using the same connection strings, as in the following example:

<?php
$before_conn1 = microtime(true);
$db1 = pg_connect($conn_string);

$before_conn2 = microtime(true);
$db2 = pg_connect($conn_string);
$after_conn2 = microtime(true);

echo($before_conn2 - $before_conn1); // Takes ~0.03s
echo("\n");
echo($after_conn2 - $before_conn2); // Takes 0s
?>

...as nice as it would have been, this does not hold true for async connections; you have to manage those yourself and you can't follow up an async connection with a blocking one later on as an easy way to wait for the connection process to complete before sending queries.

<?php
$before_conn1 = microtime(true);
$db1 = pg_connect($conn_string, PGSQL_CONNECT_ASYNC);
sleep(1);

$before_conn2 = microtime(true);
$db2 = pg_connect($conn_string);
$after_conn2 = microtime(true);

echo($before_conn2 - $before_conn1); // Takes ~1s
echo("\n");
echo($after_conn2 - $before_conn2); // Takes ~0.025s
?>

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Anonymous ¶

18 years ago

The values accepted by pg_connect's sslmode argument are: disable, allow, prefer, require

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leace at post dot cz ¶

23 years ago

If you use PostgreSQL users for authenticating into your pg database rather than using your own authentication, always specify host directive in pg_connect and edit pg_hba.conf to authenticate from this host accordingly. Otherwise, PHP will connect as 'local' using UNIX domain sockets, which is set in pg_hba.conf to 'trust' by default (so you can connect using psql on console without specifying password) and everyone can connect to db _without password_ .

down

-2

gutostraube at gmail dot com ¶

14 years ago

It's possible connect to a PostgreSQL database via Unix socket using the pg_connect() function by the following two ways:

1) Using the socket path:

<?php
$conn = pg_connect('host=/var/run/postgresql user=username dbname=databasename');
?>

2) Omitting the host name/path:

<?php
$conn = pg_connect('user=username dbname=databasename');
?>

Note: in this case (omitting the host value), the default socket path will be used.

down

-1

phpnet at benjamin dot schulz dot name ¶

19 years ago

if you need to open a new connection handle (i.e. for multiple pg_send_query()) use PGSQL_CONNECT_FORCE_NEW as second parameter to pg_connect()

down

-1

jtate at php dot net ¶

20 years ago

If you use host=HOSTNAME in your pg_connect string when connecting to PostgreSQL databases newer than 7.1, you need to make sure that your postmaster daemon is started with the "-i" option.  Otherwise the connection will fail.  See http://www.postgresql.org/idocs/index.php?client-authentication.html for client authentication documentation.

down

-1

kayotix at yahoo dot com ¶

23 years ago

Little note that is buried in the install somewhere.  In Php 3, PostgreSQL support was activated by adding --with-postgresql=[DIR] to the options passed to ./configure.  With Php 4.0.2 (on Linux) the parameter was --with-pgsql.  The only place I found this was in the installing PHP on Unix section of the manual.

down

-2

floriparob at gmail dot com ¶

7 years ago

Using the "service" parameter as the connection string -- we found that the following functions:-

putenv("PGSERVICEFILE=/path/to/your/service/file/pg_service.conf");
$connect_string = ("service=testdb");
try {
   $pgconn_handle = pg_connect($connect_string);
   . . . . . etc.

Note:-
1) the environment variable has to point to the path AND file name.
2) the file has to be readable by Apache.

See:-

https://www.postgresql.org/docs/9.6/static/libpq-pgservice.html

for how to create your pg_service.conf

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-4

Sohel Taslim ¶

16 years ago

I got the same problem but I have to solve that in different way.
In my postgresql.conf file the following was commented.
So, I active that under Connection Settings-

# - Connection Settings –
tcpip_socket = true

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-8

Anonymous ¶

8 years ago

If you get the following warning :
"Warning: pg_connect(): Unable to connect to PostgreSQL server: could not translate host name "server.your.trying.to.connect.to" to address:"
and the server you are trying to connect to is fine and the connecting itself should be working fine,
it might be the case that the postgres extension for PHP might be confused about something.
Try to restart your Apache to reinitialize the extension.

down

-2

xzilla at users dot sourceforge dot net ¶

19 years ago

regarding the note from  matias at nospam dot projectcast dot com
on 12-Feb-2002 01:16, you do not need a user in the database with the same name a your web user with ANY version of postgresql.  The only time that would be a requirement ifs if you set your postgresql server to only allow IDENT based authentication  (which IIRC is the default on Red Hat systems, which might be what lead to the confusion).  For more info on the various authentication methods allowed by postgresql, check out http://www.postgresql.org/docs/7.4/static/client-authentication.html

down

-9

Cybertinus ¶

19 years ago

If you use pg_connect('host=localhost port=5432 user=my_username password=my_password dbname=my_dbname') and you get the following error:
"Warning: pg_connect(): Unable to connect to PostgreSQL server: could not connect to server: Connection refused Is the server running on host localhost and accepting TCP/IP connections on port 5432?"
then you should try to leave the host= and port= parts out of the connection string. This sounds strange, but this is an "option" of Postgre. If you have not activated the TCP/IP port in postgresql.conf then postgresql doesn't accept any incoming requests from an TCP/IP port. If you use host= in your connection string you are going to connect to Postgre via TCP/IP, so that's not going to work. If you leave the host= part out of your connection string you connect to Postgre via the Unix domain sockets, which is faster and more secure, but you can't connect with the database via any other PC as the localhost.

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-5

derry at siliconriver.com dot au ¶

20 years ago

pg_connect seems to support SSL connections, on systems where Postgres has been compiled with ssl, i'm assuming this is since psql uses libpq to connect.
pg_connect can successfully connect, and use the "requiressl" argument.

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-3

rolf at sir-wum dot de ¶

22 years ago

pg_connect() won't work with the authentication method 'crypt' in the pg_hba.conf. Took me an hour to figure that out till I remeberd some other issues with windows missing the crypt() call.

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-9

xourge ¶

16 years ago

remember that when you use a blank password there will be an error because of:
password= dbname= (...)
to fix this problem use '' in your $options variable
example:

$options = " host='localhost' port='5432' user='postgres' password='' dbname='test' ";
pg_connect($options);

*** careful: I used double ' after password=, not "

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-5

borovik -at- gmail ¶

16 years ago

"If you use pg_connect('host=localhost port=5432 user=my_username password=my_password dbname=my_dbname') and you get the following error:
"Warning: pg_connect(): Unable to connect to PostgreSQL server: could not connect to server: Connection refused Is the server running on host localhost and accepting TCP/IP connections on port 5432?"
"
I solved this error just by setting listen_addresses = '*' in the postgresql.conf file. This error occurs probably despite of a name resolution to localhost, given in the "host" parameter. So you can set the host in the pg_connect() function.

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-16

dreamsoundaudio at gmail dot com ¶

12 years ago

Ubuntu/Debian users, specifically server versions: If you used Tasksel to build PostgreSQL, and you're banging your head against the wall with the "Fatal error: Call to undefined function pg_connect()" error, check that php5-pgsql is installed. 

Tasksel apparently doesn't install it.

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-14

Anonymous ¶

5 years ago

<?php

class Baza {
    const DNS='mysql:host=localhost;dbname=news;charset=utf8';
    const UZYTKOWNIK='root';
    const HASLO='';
    
    public $klient;
    
    function __construct(){
        $this->polacz();
    }
    public function polacz(){
    try{
        $this->klient=new PDO(
            self::DNS,
            self::UZYTKOWNIK,
            self::HASLO
        );
    }
    catch (PDOException $e){
        die('Wystąpił następujący błąd bazy danych: '.$e->getMessage());
    }
    return true;
    }
}

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-26

infotirona at yahoo dot com ¶

13 years ago

It's strange how this "Fatal error: Call to undefined function pg_connect()" happens(when everything else is OK) in PHP version 5.3.3. 

I was trying to connect to my db when I got that error message the firs time. My extensions path was OK, pgsql extension  should have been loaded from php.ini(i had enabled it before), Apache started-up without errors, but i still had the "Fatal error: Call to undefined function pg_connect()" message when i tried to connect. 
Seaching a bit around i found something about dll libraries not working as they should, so deleted the new 5.3.3 version, downloaded the PHP 5.2.5 and configured it.

I'm using Windows XP Home SP3, Apache 2.2, PHP 5.2.5 and everything works fine now... ;)

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