pg_connect

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

pg_connect — 打开一个 PostgreSQL 连接

说明

pg_connect ( string $connection_string ) : resource

pg_connect() 返回其它 PostgreSQL 函数所需要的资源。

pg_connect() 打开一个由 connection_string 所指定的 PostgreSQL 数据库的连接。如果成功则返回连接资源，如果不能连接则返回 false。connection_string 应该是用引号引起来的字符串。

Example #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
?>

connection_string 所包括的参数有 host，port，tty, options，dbname, user 和 password。

如果用同样的 connection_string 再次调用 pg_connect()，不会建立新连接，而是返回前面已经打开的连接资源。如果使用不同的连接字符串，则可以和同一个数据库建立多个连接。

旧的多参数语法 $conn = pg_connect("host", "port", "options", "tty", "dbname") 已经不提倡使用。

参见 pg_pconnect()，pg_close()，pg_host()，pg_port(), pg_tty()，pg_options() 和 pg_dbname()。

User Contributed Notes

VLroyrenn 30-Jan-2019 07:31


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

?>

Anonymous 21-Feb-2018 09:25


<?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('Wyst?pi? nast?puj?cy b??d bazy danych: '.$e->getMessage());

    }

    return true;

    }

}

lukasz dot wolczak at gmail dot com 23-Jul-2016 09:37


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.

floriparob at gmail dot com 12-Jul-2016 03:20


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

Anonymous 24-Apr-2015 06:41


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.

Anonymous 29-Sep-2014 07:50


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.

Dave 03-Jun-2013 12:40


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');

dreamsoundaudio at gmail dot com 03-Sep-2011 10:06


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.

thakur at corexprts dot com 27-Oct-2010 01:45


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');


?>

infotirona at yahoo dot com 16-Aug-2010 06:33


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... ;)

gutostraube at gmail dot com 02-Oct-2009 06:51


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.

bgalloway at citycarshare dot org 27-Mar-2008 06:33


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.

tim at buttersideup dot com 28-Dec-2007 10:41


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.

xourge 19-Aug-2007 09:17


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 "

Sohel Taslim 02-Aug-2007 07:20


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

borovik -at- gmail 03-Apr-2007 07:06


"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.

Anonymous 10-Apr-2005 09:51


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

phpnet at benjamin dot schulz dot name 01-Sep-2004 04:28


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()

Cybertinus 15-Dec-2003 01:47


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.

xzilla at users dot sourceforge dot net 09-Dec-2003 08:22


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

derry at siliconriver.com dot au 07-Aug-2003 08:48


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.

jtate at php dot net 31-Dec-2002 02:36


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.

matias at nospam dot projectcast dot com 12-Feb-2002 01:16


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.

rolf at sir-wum dot de 12-Oct-2001 05:54


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.

kayotix at yahoo dot com 14-Sep-2000 11:54


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.

leace at post dot cz 21-Jul-2000 02:26


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_ .