LXXIX. PostgreSQL functions

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.

PostgreSQL database is Open Source product and available without cost. To use PostgreSQL support, you need PostgreSQL 6.5 or later. PostgreSQL 7.0 or later to enable all PostgreSQL module feature. PostgreSQL supports many character encoding including multibyte character encoding. The current version and more information about PostgreSQL is available at http://www.postgresql.org/.

In order to enable PostgreSQL support, --with-pgsql[=DIR] is required when you compile PHP. If shared object module is available, PostgreSQL module may be loaded using extension directive in php.ini or dl() function. Supported ini directives are described in php.ini-dist which comes with source distribution.

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 use newer libpq than PostgreSQL Server to be connected. 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".

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.

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

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.