Introduction
PostgreSQL database is Open Source product and available without
cost. Postgres, developed originally in the UC Berkeley Computer Science
Department, pioneered many of the object-relational concepts now
becoming available in some commercial databases. It provides
SQL92/SQL99 language support, transaction integrity and type
extensibility. PostgreSQL is an open source descendant of this
original Berkeley code.
Requirements
To use PostgreSQL support, you need PostgreSQL 6.5 or
later, PostgreSQL 7.0 or later to enable all PostgreSQL module
features. PostgreSQL supports many character encoding including
multibyte character encoding. The current version and more
information about PostgreSQL is available at http://www.postgresql.org/.
Installation
In order to enable PostgreSQL support,
--with-pgsql[=DIR] is required when you compile
PHP. DIR is the PostgreSQL base install directory, defaults to
/usr/local/pgsql. If shared object module is
available, PostgreSQL module may be loaded using
extension directive in php.ini or
dl()
function.
Runtime Configuration
The behaviour of these functions is affected by settings in php.ini.
Table 1. PostgreSQL configuration options
| Name | Default | Changeable |
|---|
| pgsql.allow_persistent | "1" | PHP_INI_SYSTEM |
| pgsql.max_persistent | "-1" | PHP_INI_SYSTEM |
| pgsql.max_links | "-1" | PHP_INI_SYSTEM |
| pgsql.auto_reset_persistent | "0" | PHP_INI_SYSTEM |
| pgsql.ignore_notice | "0" | PHP_INI_ALL |
| pgsql.log_notice | "0" | PHP_INI_ALL |
For further details and definition of the PHP_INI_* constants see
ini_set().
Here is a short explanation of the configuration directives.
- pgsql.allow_persistent
boolean
Whether to allow persistent Postgres connections.
- pgsql.max_persistent
integer
The maximum number of persistent Postgres connections per
process.
- pgsql.max_links
integer
The maximum number of Postgres connections per process,
including persistent connections.
How to use and hints
| Warning |
Using the PostgreSQL module with PHP 4.0.6 is not recommended due to
a bug in the notice message handling code. Use 4.1.0 or later.
|
| Warning |
PostgreSQL function names will be changed in 4.2.0 release to
confirm to current coding standards. Most of new names will have
additional underscores, e.g. pg_lo_open(). Some functions are
renamed to different name for consistency. e.g. pg_exec() to
pg_query(). Older names can be used in 4.2.0 and a few releases
from 4.2.0, but they may be deleted in the future.
Table 2. Function names changed
The old pg_connect()/pg_pconnect()
syntax will be deprecated to support asynchronous connections in the
future. Please use a connection string for pg_connect()
and pg_pconnect().
|
Not all functions are supported by all builds. It depends on your
libpq (The PostgreSQL C Client interface) version and how libpq is
compiled. If there is missing function, libpq does not support
the feature required for the function.
It is also important that you do not use an older libpq than the PostgreSQL
Server to which you will be connecting. If you use libpq older than PostgreSQL
Server expects, you may have problems.
Since version 6.3 (03/02/1998) PostgreSQL uses unix domain sockets
by default. TCP port will NOT be opened by default. A table is
shown below describing these new connection possibilities. This
socket will be found in /tmp/.s.PGSQL.5432.
This option can be enabled with the '-i' flag to
postmaster and it's meaning is: "listen on
TCP/IP sockets as well as Unix domain sockets".
Table 3. Postmaster and PHP
| Postmaster | PHP | Status |
|---|
| postmaster & | pg_connect("dbname=MyDbName"); | OK |
| postmaster -i & | pg_connect("dbname=MyDbName"); | OK |
| postmaster & | pg_connect("host=localhost dbname=MyDbName"); |
Unable to connect to PostgreSQL server: connectDB() failed:
Is the postmaster running and accepting TCP/IP (with -i)
connection at 'localhost' on port '5432'? in
/path/to/file.php on line 20.
|
| postmaster -i & | pg_connect("host=localhost dbname=MyDbName"); | OK |
A connection to PostgreSQL server can be established with the
following value pairs set in the command string: $conn =
pg_connect("host=myHost port=myPort tty=myTTY options=myOptions
dbname=myDB user=myUser password=myPassword ");
The previous syntax of:
$conn = pg_connect ("host", "port", "options", "tty", "dbname")
has been deprecated.
Environmental variables affect PostgreSQL server/client
behavior. For example, PostgreSQL module will lookup PGHOST
environment variable when the hostname is omitted in the connection
string. Supported environment variables are different from version
to version. Refer to PostgreSQL Programmer's Manual (libpq -
Environment Variables) for details.
Make sure you set environment variables for appropriate user. Use
$_ENV or getenv() to check
which environment variables are available to the current process.
Example 1. Setting default parameters PGHOST=pgsql.example.com
PGPORT=7890
PGDATABASE=web-system
PGUSER=web-user
PGPASSWORD=secret
PGDATESTYLE=ISO
PGTZ=JST
PGCLIENTENCODING=EUC-JP
export PGHOST PGPORT PGDATABASE PGUSER PGPASSWORD PGDATESTYLE PGTZ PGCLIENTENCODING |
|
Predefined Constants
The constants below are defined by this extension, and
will only be available when the extension has either
been compiled into PHP or dynamically loaded at runtime.
Examples
Starting with PostgreSQL 7.1.0, you can store up to 1GB into a
field of type text. In older versions, this was limited to the block
size (default was 8KB, maximum was 32KB, defined at compile time)
To use the large object (lo) interface, it is required to enclose
large object functions within a transaction block. A transaction
block starts with a SQL statement BEGIN and if
the transaction was valid ends with COMMIT or
END. If the transaction fails the transaction
should be closed with ROLLBACK or
ABORT.
Example 2. Using Large Objects <?php
$database = pg_connect ("dbname=jacarta");
pg_query ($database, "begin");
$oid = pg_lo_create ($database);
echo "$oid\n";
$handle = pg_lo_open ($database, $oid, "w");
echo "$handle\n";
pg_lo_write ($handle, "large object data");
pg_lo_close ($handle);
pg_query ($database, "commit");
?> |
|
You should not close the connection to the PostgreSQL server
before closing the large object.
