CXXVII. 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 8.0 or later to enable all PostgreSQL module features. PostgreSQL supports many character encodings including multibyte character encoding. The current version and more information about PostgreSQL is available at http://www.postgresql.org/ and the PostgreSQL Documentation.

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	Changelog
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	Available since PHP 4.2.0.
pgsql.ignore_notice	"0"	PHP_INI_ALL	Available since PHP 4.3.0.
pgsql.log_notice	"0"	PHP_INI_ALL	Available since PHP 4.3.0.

For further details and definitions of the PHP_INI_* constants, see the Appendix I.

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.

Resource Types

There are two resource types used in the PostgreSQL module. The first one is the link identifier for a database connection, the second a resource which holds the result of a query.

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): Passed to pg_fetch_array(). Return an associative array of field names and values.
PGSQL_NUM (integer): Passed to pg_fetch_array(). Return a numerically indexed array of field numbers and values.
PGSQL_BOTH (integer): Passed to pg_fetch_array(). Return an array of field values that is both numerically indexed (by field number) and associated (by field name).
PGSQL_CONNECT_FORCE_NEW (integer): Passed to pg_connect() to force the creation of a new connection, rather then re-using an existing identical connection.
PGSQL_CONNECTION_BAD (integer): Returned by pg_connection_status() indicating that the database connection is in an invalid state.
PGSQL_CONNECTION_OK (integer): Returned by pg_connection_status() indicating that the database connection is in a valid state.
PGSQL_SEEK_SET (integer): Passed to pg_lo_seek(). Seek operation is to begin from the start of the object.
PGSQL_SEEK_CUR (integer): Passed to pg_lo_seek(). Seek operation is to begin from the current position.
PGSQL_SEEK_END (integer): Passed to pg_lo_seek(). Seek operation is to begin from the end of the object.
PGSQL_EMPTY_QUERY (integer): Returned by pg_result_status(). The string sent to the server was empty.
PGSQL_COMMAND_OK (integer): Returned by pg_result_status(). Successful completion of a command returning no data.
PGSQL_TUPLES_OK (integer): Returned by pg_result_status(). Successful completion of a command returning data (such as a SELECT or SHOW).
PGSQL_COPY_OUT (integer): Returned by pg_result_status(). Copy Out (from server) data transfer started.
PGSQL_COPY_IN (integer): Returned by pg_result_status(). Copy In (to server) data transfer started.
PGSQL_BAD_RESPONSE (integer): Returned by pg_result_status(). The server's response was not understood.
PGSQL_NONFATAL_ERROR (integer): Returned by pg_result_status(). A nonfatal error (a notice or warning) occurred.
PGSQL_FATAL_ERROR (integer): Returned by pg_result_status(). A fatal error occurred.
PGSQL_TRANSACTION_IDLE (integer): Returned by pg_transaction_status(). Connection is currently idle, not in a transaction.
PGSQL_TRANSACTION_ACTIVE (integer): Returned by pg_transaction_status(). A command is in progress on the connection. A query has been sent via the connection and not yet completed.
PGSQL_TRANSACTION_INTRANS (integer): Returned by pg_transaction_status(). The connection is idle, in a transaction block.
PGSQL_TRANSACTION_INERROR (integer): Returned by pg_transaction_status(). The connection is idle, in a failed transaction block.
PGSQL_TRANSACTION_UNKNOWN (integer): Returned by pg_transaction_status(). The connection is bad.
PGSQL_DIAG_SEVERITY (integer): Passed to pg_result_error_field(). The severity; the field contents are ERROR, FATAL, or PANIC (in an error message), or WARNING, NOTICE, DEBUG, INFO, or LOG (in a notice message), or a localized translation of one of these. Always present.
PGSQL_DIAG_SQLSTATE (integer): Passed to pg_result_error_field(). The SQLSTATE code for the error. The SQLSTATE code identifies the type of error that has occurred; it can be used by front-end applications to perform specific operations (such as error handling) in response to a particular database error. This field is not localizable, and is always present.
PGSQL_DIAG_MESSAGE_PRIMARY (integer): Passed to pg_result_error_field(). The primary human-readable error message (typically one line). Always present.
PGSQL_DIAG_MESSAGE_DETAIL (integer): Passed to pg_result_error_field(). Detail: an optional secondary error message carrying more detail about the problem. May run to multiple lines.
PGSQL_DIAG_MESSAGE_HINT (integer): Passed to pg_result_error_field(). Hint: an optional suggestion what to do about the problem. This is intended to differ from detail in that it offers advice (potentially inappropriate) rather than hard facts. May run to multiple lines.
PGSQL_DIAG_STATEMENT_POSITION (integer): Passed to pg_result_error_field(). A string containing a decimal integer indicating an error cursor position as an index into the original statement string. The first character has index 1, and positions are measured in characters not bytes.
PGSQL_DIAG_INTERNAL_POSITION (integer): Passed to pg_result_error_field(). This is defined the same as the PG_DIAG_STATEMENT_POSITION field, but it is used when the cursor position refers to an internally generated command rather than the one submitted by the client. The PG_DIAG_INTERNAL_QUERY field will always appear when this field appears.
PGSQL_DIAG_INTERNAL_QUERY (integer): Passed to pg_result_error_field(). The text of a failed internally-generated command. This could be, for example, a SQL query issued by a PL/pgSQL function.
PGSQL_DIAG_CONTEXT (integer): Passed to pg_result_error_field(). An indication of the context in which the error occurred. Presently this includes a call stack traceback of active procedural language functions and internally-generated queries. The trace is one entry per line, most recent first.
PGSQL_DIAG_SOURCE_FILE (integer): Passed to pg_result_error_field(). The file name of the PostgreSQL source-code location where the error was reported.
PGSQL_DIAG_SOURCE_LINE (integer): Passed to pg_result_error_field(). The line number of the PostgreSQL source-code location where the error was reported.
PGSQL_DIAG_SOURCE_FUNCTION (integer): Passed to pg_result_error_field(). The name of the PostgreSQL source-code function reporting the error.
PGSQL_ERRORS_TERSE (integer): Passed to pg_set_error_verbosity(). Specified that returned messages include severity, primary text, and position only; this will normally fit on a single line.
PGSQL_ERRORS_DEFAULT (integer): Passed to pg_set_error_verbosity(). The default mode produces messages that include the above plus any detail, hint, or context fields (these may span multiple lines).
PGSQL_ERRORS_VERBOSE (integer): Passed to pg_set_error_verbosity(). The verbose mode includes all available fields.
PGSQL_STATUS_LONG (integer): Passed to pg_result_status(). Indicates that numerical result code is desired.
PGSQL_STATUS_STRING (integer): Passed to pg_result_status(). Indicates that textual result command tag is desired.
PGSQL_CONV_IGNORE_DEFAULT (integer): Passed to pg_convert(). Ignore default values in the table during conversion.
PGSQL_CONV_FORCE_NULL (integer): Passed to pg_convert(). Use SQL NULL in place of an empty string.
PGSQL_CONV_IGNORE_DEFAULT (integer): Passed to pg_convert(). Ignore conversion of NULL into SQL NOT NULL columns.

Notes

Note: Not all functions are supported by all builds. It depends on your libpq (The PostgreSQL C client library) version and how libpq is compiled. If PHP PostgreSQL extensions are missing, then it is because your libpq version does not support them.

Note: Most PostgreSQL functions accept connection as the first optional parameter. If it is not provided, the last opened connection is used. If it doesn't exist, functions return FALSE.

Note: PostgreSQL automatically folds all identifiers (e.g. table/column names) to lower-case values at object creation time and at query time. To force the use of mixed or upper case identifiers, you must escape the identifier using double quotes ("").

Note: PostgreSQL does not have special commands for fetching database schema information (eg. all the tables in the current database). Instead, there is a standard schema named information_schema in PostgreSQL 7.4 and above containing system views with all the necessary information, in an easily queryable form. See the PostgreSQL Documentation for full details.

Examples

This simple example shows how to connect, execute a query, print resulting rows and disconnect from a PostgreSQL database.

Example 1. PostgreSQL extension overview example


<?php
// Connecting, selecting database
$dbconn = pg_connect("host=localhost dbname=publishing user=www password=foo")
    or die('Could not connect: ' . pg_last_error());

// Performing SQL query
$query = 'SELECT * FROM authors';
$result = pg_query($query) or die('Query failed: ' . pg_last_error());

// Printing results in HTML
echo "<table>\n";
while ($line = pg_fetch_array($result, null, PGSQL_ASSOC)) {
    echo "\t<tr>\n";
    foreach ($line as $col_value) {
        echo "\t\t<td>$col_value</td>\n";
    }
    echo "\t</tr>\n";
}
echo "</table>\n";

// Free resultset
pg_free_result($result);

// Closing connection
pg_close($dbconn);
?>

Table of Contents
pg_affected_rows -- Returns number of affected records (tuples)
pg_cancel_query -- Cancel an 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 values 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 a string for insertion into a bytea field
pg_escape_string -- Escape a string for insertion into a text field
pg_execute -- Sends a request to execute a prepared statement with given parameters, and waits for the result.
pg_fetch_all_columns -- Fetches all rows in a particular result column as an array
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 SQL 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_table -- Returns the name or oid of the tables field
pg_field_type_oid -- Returns the type ID (OID) for the corresponding field number
pg_field_type -- Returns the type name for the corresponding field number
pg_free_result -- Free result memory
pg_get_notify -- Gets SQL NOTIFY message
pg_get_pid -- Gets the backend's process ID
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 row'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 within a large object
pg_lo_tell -- Returns current seek position a of large object
pg_lo_unlink -- Delete a large object
pg_lo_write -- Write to a large object
pg_meta_data -- Get meta data for table
pg_num_fields -- Returns the number of fields in a result
pg_num_rows -- Returns the number of rows in a result
pg_options -- Get the options associated with the connection
pg_parameter_status -- Looks up a current parameter setting of the server.
pg_pconnect -- Open a persistent PostgreSQL connection
pg_ping -- Ping database connection
pg_port -- Return the port number associated with the connection
pg_prepare -- Submits a request to create a prepared statement with the given parameters, and waits for completion.
pg_put_line -- Send a NULL-terminated string to PostgreSQL backend
pg_query_params -- Submits a command to the server and waits for the result, with the ability to pass parameters separately from the SQL command text.
pg_query -- Execute a query
pg_result_error_field -- Returns an individual field of an error report.
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_execute -- Sends a request to execute a prepared statement with given parameters, without waiting for the result(s).
pg_send_prepare -- Sends a request to create a prepared statement with the given parameters, without waiting for completion.
pg_send_query_params -- Submits a command and separate parameters to the server without waiting for the result(s).
pg_send_query -- Sends asynchronous query
pg_set_client_encoding -- Set the client encoding
pg_set_error_verbosity -- Determines the verbosity of messages returned by pg_last_error() and pg_result_error().
pg_trace -- Enable tracing a PostgreSQL connection
pg_transaction_status -- Returns the current in-transaction status of the server.
pg_tty -- Return the TTY name associated with the connection
pg_unescape_bytea -- Unescape binary for bytea type
pg_untrace -- Disable tracing of a PostgreSQL connection
pg_update -- Update table
pg_version -- Returns an array with client, protocol and server version (when available)