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# LXIII. MySQL Functions

# Introduction

These functions allow you to access MySQL database servers. More information about MySQL can be found at http://www.mysql.com/.

Documentation for MySQL can be found at http://www.mysql.com/documentation/.

# Requirements

In order to have these functions available, you must compile PHP with MySQL support.

# Installation

By using the `--with-mysql` configuration option you enable PHP to access MySQL databases. If you use this option without specifying the path to MySQL, PHP will use the built-in MySQL client libraries. With PHP4 MySQL support is always enabled; if you don't specify the configure option, the bundled libraries are used. Users who run other applications that use MySQL (for example, running PHP 3 and PHP 4 as concurrent apache modules, or auth-mysql) should always specify the path to MySQL: `--with-mysql=/path/to/mysql`. This will force PHP to use the client libraries installed by MySQL, avoiding any conflicts.

Warning
Crashes and startup problems of `PHP` may be encountered when loading this extension in conjunction with the recode extension. See the recode extension for more information.

# Runtime Configuration

The behaviour of these functions is affected by settings in `php.ini`.

Table 1. MySQL Configuration Options

Name | Default | Changeable
--- | --- | ---
mysql.allow_persistent | "On" | PHP_INI_SYSTEM
mysql.max_persistent | "-1" | PHP_INI_SYSTEM
mysql.max_links | "-1" | PHP_INI_SYSTEM
mysql.default_port | NULL | PHP_INI_ALL
mysql.default_socket | NULL | PHP_INI_ALL
mysql.default_host | NULL | PHP_INI_ALL
mysql.default_user | NULL | PHP_INI_ALL
mysql.default_password | NULL | PHP_INI_ALL
mysql.connect_timeout | "0" | PHP_INI_SYSTEM

For further details and definition of the PHP_INI_* constants see ini_set().

Here is a short explanation of the configuration directives.

`mysql.allow_persistent` boolean

  Whether to allow persistent connections to MySQL.

`mysql.max_persistent` integer

  The maximum number of persistent MySQL connections per process.

`mysql.max_links` integer

  The maximum number of MySQL connections per process, including persistent connections.

`mysql.default_port` string

  The default TCP port number to use when connecting to the database server if no other port is specified. If no default is specified, the port will be obtained from the `MYSQL_TCP_PORT` environment variable, the `mysql-tcp` entry in `/etc/services` or the compile-time `MYSQL_PORT` constant, in that order. Win32 will only use the `MYSQL_PORT` constant.

`mysql.default_socket` string

  The default socket name to use when connecting to a local database server if no other socket name is specified.

`mysql.default_host` string

  The default server host to use when connecting to the database server if no other host is specified. Doesn't apply in safe mode.

`mysql.default_user` string

  The default user name to use when connecting to the database server if no other name is specified. Doesn't apply in safe mode.

`mysql.default_password` string

  The default password to use when connecting to the database server if no other password is specified. Doesn't apply in safe mode.

`mysql.connect_timeout` integer

  Connect timeout in seconds. On Linux this timeout is also used for waiting for the first answer from the server.

# Resource Types

There are two resource types used in the MySQL 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.

Since PHP 4.3.0 it is possible to specify additional client flags for the mysql_connect() and mysql_pconnect() functions. The following constants are defined:

Table 2. MySQL client constants

constant | description
--- | ---
MYSQL_CLIENT_COMPRESS | use compression protocol
MYSQL_CLIENT_IGNORE_SPACE | Allow space after function names
MYSQL_CLIENT_INTERACTIVE | Allow interactive_timeout seconds (instead of wait_timeout) of inactivity before closing the connection.

The function mysql_fetch_array() uses a constant for the different types of result arrays. The following constants are defined:

Table 3. MySQL fetch constants

constant | description
--- | ---
MYSQL_ASSOC | Columns are returned into the array having the fieldname as the array index.
MYSQL_BOTH | Columns are returned into the array having both a numerical index and the fieldname as the array index.
MYSQL_NUM | Columns are returned into the array having a numerical index to the fields. This index starts with 0, the first field in the result.

# Examples

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

Example 1. MySQL extension overview example

    <?php
        /* Connecting, selecting database */
        $link = mysql_connect("mysql_host", "mysql_user", "mysql_password")
            or die("Could not connect");
        print "Connected successfully";
        mysql_select_db("my_database") or die("Could not select database");

        /* Performing SQL query */
        $query = "SELECT * FROM my_table";
        $result = mysql_query($query) or die("Query failed");

        /* Printing results in HTML */
        print "<table>\n";
        while ($line = mysql_fetch_array($result, MYSQL_ASSOC)) {
            print "\t<tr>\n";
            foreach ($line as $col_value) {
                print "\t\t<td>$col_value</td>\n";
            }
            print "\t</tr>\n";
        }
        print "</table>\n";

        /* Free resultset */
        mysql_free_result($result);

        /* Closing connection */
        mysql_close($link);
    ?>

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