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# LXXVIII. PostgreSQL functions

Warning
Use of PostgreSQL module with PHP 4.0.6 is not recommended due to a bug in notice message handling.

Warning
PostgreSQL function names will be changed in 4.2.0 release to confirm current coding standard. Most of new names will have additional under score(s), e.g. pg_lo_open(). Some functions are renamed to different name for consistency. e.g. pg_exec() to pg_query(). Older names may be used in 4.2.0 and a few releases from 4.2.0, but they may be deleted in the future. CVS version has new function names. Obsolete pg_connect()/pg_pconnect() may be depreciated to support async connect feature in the future.

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/SQL3 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 charactor encoding including multibyte character encoding. The current version and more information about PostgreSQL is available at www.postgresql.org.

In order to enable PostgreSQL support, "--enable-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 file which comes with source distribution.

Not all functions are supported by all builds. It depends on your libpq (The PostgreSQL C Client interface) versoin 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 openned 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 1. 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 variable affects PostgreSQL server/client behavior. For example, PostgreSQL module will lookup PGHOST environment variable when hostname is omitted in connection string. Supported environment variables are different from version to version. Refer to PostgreSQL Programmer's Manual (libpq - Environment Variables) for details.

From PostgreSQL 7.1.0, text data type has 1GB as its max size. Older PostgreSQL's text data type is limitted by block size. (Default 8KB. Max 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 1. Using Large Objects
    <?php
        $database = pg_connect ("dbname=jacarta");
        pg_exec ($database, "begin");
        $oid = pg_locreate ($database);
        echo ("$oid\n");
        $handle = pg_loopen ($database, $oid, "w");
        echo ("$handle\n");
        pg_lowrite ($handle, "large object data");
        pg_loclose ($handle);
        pg_exec ($database, "commit");
    ?>

Do not close connection resource before closing large object resource.

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