Register a settings field to a settings page and section.
This is part of the Settings API, which lets you automatically generate wp-admin settings pages by registering your settings and using a few callbacks to control the output.
This function assumes you already know the settings
$page and the page
$section that the field should be shown on.
You MUST register any options used by this function with register_setting() or they won't be saved and updated automatically.
The callback function needs to output the appropriate html input and fill it with the old value, the saving will be done behind the scenes.
This function can also be used to add extra settings fields to the default WP settings pages like media or general. You can add them to an existing section, or use add_settings_section() to create a new section to add the fields to.
See Settings API for details.
<?php add_settings_field( $id, $title, $callback, $page, $section, $args ); ?>
Adds a setting with id "myprefix_setting-id" to the General Settings page. "myprefix" should be a unique string for your plugin or theme. Sets a label so that the setting title can be clicked on to focus on the field.
add_settings_field( 'myprefix_setting-id', 'This is the setting title', 'myprefix_setting_callback_function', 'general', 'myprefix_settings-section-name', array( 'label_for' => 'myprefix_setting-id' ) );
add_settings_field() is located in