LXXXII. PostgreSQL functions
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, transactions, referential integrity,
stored procedures and type extensibility. PostgreSQL is an open source
descendant of this original Berkeley code.
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
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
The behaviour of these functions is affected by settings in php.ini.
Table 1. PostgreSQL configuration options
For further details and definition of the PHP_INI_* constants see
Here's a short explanation of
the configuration directives.
Whether to allow persistent Postgres connections.
The maximum number of persistent Postgres connections per
The maximum number of Postgres connections per process,
including persistent connections.
Detect broken persistent links with pg_pconnect().
Needs a little overhead.
Whether or not to ignore PostgreSQL backend notices.
Whether or not to log PostgreSQL backends notice messages. The PHP
pgsql.ignore_notice must be off in order to log notice
How to use and hints
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.
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()
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 -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
export PGHOST PGPORT PGDATABASE PGUSER PGPASSWORD PGDATESTYLE PGTZ PGCLIENTENCODING
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.
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
Example 2. Using Large Objects
$database = pg_connect ("dbname=jacarta");
pg_query ($database, "begin");
$oid = pg_lo_create ($database);
$handle = pg_lo_open ($database, $oid, "w");
pg_lo_write ($handle, "large object data");
pg_query ($database, "commit");
You should not close the connection to the PostgreSQL server
before closing the large object.
add a note
User Contributed Notes
daniel at bichara dot com dot br
Running RedHat Linux and Apache with suexec enabled you must include pgsql.so on each .php file using dl("pgsql.so") and remove "extension=pgsql.so" from php.ini, otherwise Apache (httpd) will not start.
anonymous at unknown dot com
I just wanted to add to my previous post I've got the system up and running.
Environment: Windows XP, Apache 1.3.23, Php 4.3 RC2, PostGreSQL beta4 native windows build
Installation was fairly easy:
1. read the readme.txt
2. edit the setenv.bat as described in readme
3. run 'initdb'
all execs are in /bin
help is accessed like <command> --help
4. Start the psql deamon - you may want to create a batch file like
'D:\postgres_beta4\bin\postmaster -h localhost -D D:/postgres_beta4/data'
--deamon should be up and running now--
You can login into a shell from a console like
'psql -h localhost -d <username>'
You must load the postgresql extension by editing the php.ini and restarting apache in order to access psql with php.
And one final not: when running
$dbconn = pg_connect ("host=localhost port=5432 dbname=$dbname user=$user");
remember that $user and or $dbname is CASESENSITIVE.
Oh yeah, I created the data dir manually - don't know whether that was necessary
anonymous at unknown dot com
amk at eight13 dot com
The list of postgresql function name changes is missing pg_errormessage being changed to pg_last_error.
swm at php dot net
mystran at wasteland dot pp dot htv dot fi
Nice to know fact that I didn't find documented here.
PHP will return values of PostgreSQL boolean datatype as single character strings "t" and "f", not PHP true and false.
't' or 'f' is valid boolean expression for PostgreSQL.
All values from PostgreSQL are strings, since PostgreSQL integer, float may be much larger than PHP's native int, double can handle. PostgreSQL array is not supported.
saberit at home dot com
I tried compiling PHP from source with PostgreSQL support (./configure --with-pgsql=/usr/local/pgsql) and ran into a bunch of problems when trying to 'make'. The problem was that some of the PostgreSQL headers were not installed by default when I installed PostgreSQL from source. When installing PostgreSQL make sure you 'make install-all-headers' after you 'make install'.
prince_shri at yahoo dot com
in debian, you need to include
in all your scripts of php4. I think its different for PHP3 -
Debian users should be able to use "extension" directive to load pgsql.so. This method is prefered method if you use pgsql module always.
hubert at hubertmuller dot com
The best way to find the separated list of tables, sequences, keys etc is:
SELECT relname FROM pg_class WHERE relkind='<value>' AND relname !~ '^pg_';
i for keys,
r for relations,
S for sequences
Note that all tables names that begins with 'pg_' are PostgreSQL internal tables (this explain why I use AND relname !~ '^pg_' condition).
passion at monkey dot org
!spamcraig at ahdore dot com
If you want to extract data from select statements, you need to store the result index, and then apply pg_result to that value. Basically, do this
$resultIdx = pg_query ($database, "select * from tablename");
$mySelect = pg_fetch_result($resultIdx, 0, 0); // gets column 0 of tuple 0
echo("My select: [".$mySelect."]");
I'm new to php and had to do some fiddling around to work this out. It's reasonably elementary, but not demonstrated by the examples on these pages. Hopefully it will come in useful to someone else.
jdb30 at cornell.edu
bleach at chek dot com
If you want to see all the objects in a database, you can find that information in the pg_class table. <BR>
SELECT * FROM pg_class;<BR>
Now this is going to be kind of long and complex, to see how psql command handles the \d and other things. use the syntax. psql -E <Database>, ie psql -E mydatabase <BR>
What this will do is show the SQL command used for everything. So when you type a \d or something, it shows the SQL query used for the result.