config file docs

docs/config/config.md

@@ -0,0 +1,86 @@
+<!--
+    This source file is part of the open source project
+    ExpressionEngine User Guide (https://github.com/ExpressionEngine/ExpressionEngine-User-Guide)
+
+    @link      https://expressionengine.com/
+    @copyright Copyright (c) 2003-2022, Packet Tide, LLC (https://packettide.com)
+    @license   https://expressionengine.com/license Licensed under Apache License, Version 2.0
+-->
+
+# Main Configuration File
+
+The main configuration settings are stored in the form of a PHP array in the `system/user/config/config.php` file.
+
+This file is populated automatically during the installation process and contains the most important settings that are used by ExpressionEngine.
+
+Settings from this file are loaded every time the system is run. This means that [config overrides](general/system-configuration-overrides.md) set in `config.php` always affect the system’s configuration.
+
+At a minimum, this configuration file contains the following settings:
+
+#### `app_version`
+
+The installation's ExpressionEngine version. This value is set automatically and normally should not be modified. 
+
+However if you need to run an update script again, you can modify this value to a lower version number so the system would "see" the update(s) available.
+
+    $config['app_version'] = '7.4.0';
+
+#### `encryption_key`
+
+This is the secret key used by the [Encrypt service](development/services/encrypt.md) to protect sensitive data in the database. It is set automatically during the installation process. If you need to use your own key please refer to [Troubleshooting guide](troubleshooting/error-messages.md#generating-new-encryption-keys) on how to generate a new one.
+
+    $config['encryption_key'] = '26791dcd5c7cc9e569cc05b16b96235985cc9f03';
+
+#### `session_crypt_key`
+
+Similar to the `encryption_key`, but used to protected session data.
+
+    $config['session_crypt_key'] = 'd9e776dc9a5de0cd83e7c76a76756daa64ff4b8b';
+
+#### `database`
+
+The database connection details are one of the most important settings in the configuration file.  The array is required to have an element with a key of `expressionengine`, which in turn needs to be an array with the following keys:
+
+ - `hostname` - The hostname or IP address of your database server
+ - `database` - The name of the database to connect to
+ - `username` - The username used to connect to the database
+ - `password` - The password used to connect to the database
+ - `dbprefix` - The prefix used for all database tables (default is `exp_`)
+ - `char_set` - The character set used in communicating with the database (default is `utf8mb4`)
+ - `dbcollat` - The character collation used in communicating with the database (default is `utf8mb4_unicode_ci`)
+ - `port` - The port used to connect to the database (default is `3306`)
+
+    ```php
+    $config['database'] = array(
+        'expressionengine' => array(
+            'hostname' => 'localhost',
+            'database' => 'ee740',
+            'username' => 'root',
+            'password' => '',
+            'dbprefix' => 'exp_',
+            'char_set' => 'utf8mb4',
+            'dbcollat' => 'utf8mb4_unicode_ci',
+            'port'     => ''
+        ),
+    );
+    ```
+
+In addition, you can use following keys inside `expressionengine`:
+
+ - `pconnect` - Whether to use persistent connections (default is `true`)
+
+The following keys can be specified and will be converted to [PDO constants](https://www.php.net/manual/en/ref.pdo-mysql.php#pdo-mysql.constants) when passed to the database driver:
+
+ - `MYSQL_ATTR_LOCAL_INFILE`
+ - `MYSQL_ATTR_LOCAL_INFILE_DIRECTORY`
+ - `MYSQL_ATTR_READ_DEFAULT_FILE`
+ - `MYSQL_ATTR_READ_DEFAULT_GROUP`
+ - `MYSQL_ATTR_MAX_BUFFER_SIZE`
+ - `MYSQL_ATTR_INIT_COMMAND`
+ - `MYSQL_ATTR_COMPRESS`
+ - `MYSQL_ATTR_SSL_CA`
+ - `MYSQL_ATTR_SSL_CAPATH`
+ - `MYSQL_ATTR_SSL_CERT`
+ - `MYSQL_ATTR_SSL_CIPHER`
+ - `MYSQL_ATTR_SSL_KEY`
+ - `MYSQL_ATTR_SSL_VERIFY_SERVER_CERT`

docs/toc_sections/_advanced_usage_toc.yml

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 - name: Config Files
   items:
+  - name: Main Configuration File
+    href: config/config.md
   - name: System Config Overrides
     href: general/system-configuration-overrides.md
   - name: Additional Config Files