pg_connect

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

pg_connect — Открывает соединение с базой данных PostgreSQL

Описание

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

Функция pg_connect() открывает соединение с базой данных PostgreSQL на основе параметров, которые указали в строке connection_string.

При повторном вызове функции pg_connect() с теми же параметрами в строке connection_string функция вернёт подключение, которое уже установили, если только в параметр flags не передали флаг PGSQL_CONNECT_FORCE_NEW.

Прежний синтаксис с набором параметров — $conn = pg_connect("host", "port", "options", "tty", "dbname") — устарел.

Список параметров

connection_string

Параметр connection_string принимает пустую строку или настройки параметров через пробел. Каждую настройку параметра передают в форме keyword = value. Пробелы вокруг знака равенства необязательны. Пустые значения или значения с пробелами записывают в одинарных кавычках: keyword = 'a value'. Одинарные кавычки и обратные слеши внутри значения экранируют обратным слешем: \' и \\.

Функция распознаёт следующие параметры: host, hostaddr, port, dbname (значение по умолчанию для параметра user), user, password, connect_timeout, options, tty (игнорируется), sslmode, requiressl (устарело в связи с использованием параметра sslmode) и service. Поддержка параметров зависит от версии СУБД PostgreSQL.

Параметр options устанавливает параметры командной строки, которые вызовет сервер.

flags

При передаче флага PGSQL_CONNECT_FORCE_NEW функция создаёт новое соединение, даже если строка подключения connection_string идентична строке подключения, которое уже установили.

При передаче флага PGSQL_CONNECT_ASYNC функция устанавливает асинхронное соединение. Состояние соединения проверяют функцией pg_connect_poll() или pg_connection_status().

Возвращаемые значения

Функция возвращает экземпляр класса PgSql\Connection, если выполнилась успешно, или false, если возникла ошибка.

Список изменений

Версия	Описание
8.1.0	Функция теперь возвращает экземпляр класса PgSql\Connection; раньше возвращался ресурс (resource).

Примеры

Пример #1 Пример установки соединения функцией pg_connect()

<?php

// Подключение к базе данных "mary"
$dbconn = pg_connect("dbname=mary");

// Подключение к базе "mary" на хосте "localhost" и порте "5432"
$dbconn2 = pg_connect("host=localhost port=5432 dbname=mary");

// Подключение к базе "mary" на хосте "sheep" с именем пользователя и паролем
$dbconn3 = pg_connect("host=sheep port=5432 dbname=mary user=lamb password=foo");

// Подключение к базе "test" на хосте "sheep" с именем пользователя и паролем
$conn_string = "host=sheep port=5432 dbname=test user=lamb password=bar";
$dbconn4 = pg_connect($conn_string);

// Подключение к базе на хосте "localhost" с передачей параметра командной строки,
// который устанавливает кодировку UTF-8
$dbconn5 = pg_connect("host=localhost options='--client_encoding=UTF8'");

?>

Смотрите также

pg_pconnect() - Открывает постоянное соединение с сервером PostgreSQL
pg_close() - Закрывает соединение с базой данных PostgreSQL
pg_host() - Возвращает имя хоста, соответствующего подключению
pg_port() - Возвращает номер порта, соответствующий заданному соединению
pg_tty() - Возвращает имя терминала TTY, связанное с соединением
pg_options() - Получение параметров соединения с сервером баз данных
pg_dbname() - Определяет имя базы данных

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Примечания пользователей 18 notes

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lukasz dot wolczak at gmail dot com ¶

9 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 ¶

12 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 ¶

11 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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bgalloway at citycarshare dot org ¶

17 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

tim at buttersideup dot com ¶

17 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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thakur at corexprts dot com ¶

15 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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matias at nospam dot projectcast dot com ¶

23 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.

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VLroyrenn ¶

6 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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-2

Anonymous ¶

20 years ago

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

down

-2

gutostraube at gmail dot com ¶

16 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

-3

leace at post dot cz ¶

25 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

-3

phpnet at benjamin dot schulz dot name ¶

21 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

-4

Sohel Taslim ¶

18 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

down

-3

floriparob at gmail dot com ¶

9 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

down

-3

xzilla at users dot sourceforge dot net ¶

21 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

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-3

jtate at php dot net ¶

22 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.

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-4

kayotix at yahoo dot com ¶

25 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.

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-4

rolf at sir-wum dot de ¶

24 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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