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Last updated: Thu, 21 Aug 2003

LXXXII. PostgreSQL functions

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, transactions, referential integrity, stored procedures 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/ and http://techdocs.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

NameDefaultChangeable
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's 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.

pgsql.auto_reset_persistent integer

Detect broken persistent links with pg_pconnect(). Needs a little overhead.

pgsql.ignore_notice integer

Whether or not to ignore PostgreSQL backend notices.

pgsql.log_notice integer

Whether or not to log PostgreSQL backends notice messages. The PHP directive pgsql.ignore_notice must be off in order to log notice messages.

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

Old nameNew name
pg_exec()pg_query()
pg_getlastoid()pg_last_oid()
pg_cmdtuples()pg_affected_rows()
pg_numrows()pg_num_rows()
pg_numfields()pg_num_fields()
pg_fieldname()pg_field_name()
pg_fieldsize()pg_field_size()
pg_fieldnum()pg_field_num()
pg_fieldprtlen()pg_field_prtlen()
pg_fieldisnull()pg_field_is_null()
pg_freeresult()pg_free_result()
pg_result()pg_fetch_result()
pg_loreadall()pg_lo_read_all()
pg_locreate()pg_lo_create()
pg_lounlink()pg_lo_unlink()
pg_loopen()pg_lo_open()
pg_loclose()pg_lo_close()
pg_loread()pg_lo_read()
pg_lowrite()pg_lo_write()
pg_loimport()pg_lo_import()
pg_loexport()pg_lo_export()

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

PostmasterPHPStatus
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.

PGSQL_ASSOC (integer)

PGSQL_NUM (integer)

PGSQL_BOTH (integer)

PGSQL_CONNECTION_BAD (integer)

PGSQL_CONNECTION_OK (integer)

PGSQL_SEEK_SET (integer)

PGSQL_SEEK_CUR (integer)

PGSQL_SEEK_END (integer)

PGSQL_ESCAPE_STRING (integer)

PGSQL_ESCAPE_BYTEA (integer)

PGSQL_EMPTY_QUERY (integer)

PGSQL_COMMAND_OK (integer)

PGSQL_TUPLES_OK (integer)

PGSQL_COPY_OUT (integer)

PGSQL_COPY_IN (integer)

PGSQL_BAD_RESPONSE (integer)

PGSQL_NONFATAL_ERROR (integer)

PGSQL_FATAL_ERROR (integer)

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.

Table of Contents
pg_affected_rows -- Returns number of affected records (tuples)
pg_cancel_query --  Cancel asynchronous query
pg_client_encoding --  Gets the client encoding
pg_close -- Closes a PostgreSQL connection
pg_connect -- Open a PostgreSQL connection
pg_connection_busy --  Get connection is busy or not
pg_connection_reset --  Reset connection (reconnect)
pg_connection_status --  Get connection status
pg_convert --  Convert associative array value into suitable for SQL statement.
pg_copy_from --  Insert records into a table from an array
pg_copy_to --  Copy a table to an array
pg_dbname -- Get the database name
pg_delete --  Deletes records.
pg_end_copy -- Sync with PostgreSQL backend
pg_escape_bytea --  Escape binary for bytea type
pg_escape_string --  Escape string for text/char type
pg_fetch_all -- Fetches all rows from a result as an array
pg_fetch_array -- Fetch a row as an array
pg_fetch_assoc -- Fetch a row as an associative array
pg_fetch_object -- Fetch a row as an object
pg_fetch_result -- Returns values from a result resource
pg_fetch_row -- Get a row as an enumerated array
pg_field_is_null -- Test if a field is NULL
pg_field_name -- Returns the name of a field
pg_field_num -- Returns the field number of the named field
pg_field_prtlen -- Returns the printed length
pg_field_size --  Returns the internal storage size of the named field
pg_field_type --  Returns the type name for the corresponding field number
pg_free_result -- Free result memory
pg_get_notify -- Ping database connection
pg_get_pid -- Ping database connection
pg_get_result --  Get asynchronous query result
pg_host --  Returns the host name associated with the connection
pg_insert --  Insert array into table.
pg_last_error -- Get the last error message string of a connection
pg_last_notice --  Returns the last notice message from PostgreSQL server
pg_last_oid -- Returns the last object's oid
pg_lo_close -- Close a large object
pg_lo_create -- Create a large object
pg_lo_export -- Export a large object to file
pg_lo_import -- Import a large object from file
pg_lo_open -- Open a large object
pg_lo_read_all --  Reads an entire large object and send straight to browser
pg_lo_read -- Read a large object
pg_lo_seek --  Seeks position of large object
pg_lo_tell --  Returns current position of large object
pg_lo_unlink -- Delete a large object
pg_lo_write -- Write a large object
pg_meta_data --  Get meta data for table.
pg_num_fields -- Returns the number of fields
pg_num_rows -- Returns the number of rows
pg_options -- Get the options associated with the connection
pg_pconnect -- Open a persistent PostgreSQL connection
pg_ping -- Ping database connection
pg_port --  Return the port number associated with the connection
pg_put_line -- Send a NULL-terminated string to PostgreSQL backend
pg_query -- Execute a query
pg_result_error --  Get error message associated with result
pg_result_seek -- Set internal row offset in result resource
pg_result_status --  Get status of query result
pg_select --  Select records.
pg_send_query --  Sends asynchronous query
pg_set_client_encoding --  Set the client encoding
pg_trace -- Enable tracing a PostgreSQL connection
pg_tty --  Return the tty name associated with the connection
pg_unescape_bytea --  Escape binary for bytea type
pg_untrace -- Disable tracing of a PostgreSQL connection
pg_update --  Update table.


add a note add a note User Contributed Notes
PostgreSQL functions
daniel at bichara dot com dot br
31-Dec-2002 09:04
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
30-Nov-2002 01:50
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

Grtz Vargo
anonymous at unknown dot com
29-Nov-2002 10:01
Here: http://archives.postgresql.org/pgsql-hackers/2002-11/msg00375.php
you can find the announcement for a native windows PostGreSQL port that is to be released in december (no cygwin). It also tells you where to download the beta (ftp://209.61.187.152/postgres/).
amk at eight13 dot com
28-Nov-2002 03:36
The list of postgresql function name changes is missing pg_errormessage being changed to pg_last_error.
swm at php dot net
22-Aug-2002 10:49
My talk on PHP and PostgreSQL which I presented at O'Reilly OSCON 2002 is now online.

http://www.alcove.com.au/oreilly/
mystran at wasteland dot pp dot htv dot fi
04-Feb-2002 11:46
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.

[Editor's Note]
'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
15-Sep-2001 04:11
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
01-Aug-2001 04:45
in debian, you need to include

dl('pgsql.so')

in all your scripts of php4. I think its different for PHP3 -

dl('libpg.so')

[Editor's Note]
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
10-Jul-2001 06:36
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_';

<value> takes:
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
28-Jun-2001 08:53
I've tried to mimic the following mysql database connection functions for postgres.
http://www.php.net/manual/en/function.mysql-list-dbs.php
http://www.php.net/manual/en/function.mysql-list-tables.php

These are assuming that you're passing in $link as the result from pg_connect:

function pg_list_dbs($link)

    $sql = 'SELECT datname FROM pg_database';
    return (pg_query($link, $sql));


function pg_list_tables($link)

    $sql = "SELECT relname FROM pg_class WHERE relname !~ '^pg_'";
    return (pg_query($link, $sql));
}
!spamcraig at ahdore dot com
15-Apr-2001 03:11
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
07-Dec-2000 04:08
For further reading on PostgreSQL, see:
http://www.postgresql.org/docs/awbook.html
bleach at chek dot com
02-Mar-2000 04:36
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.

<posix_unamepg_affected_rows>
 Last updated: Thu, 21 Aug 2003
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