辛星浅析WordPress中的get_option

WordPress使用get_option()来获取通过option表单设置值的方法，如果数据库中不存在该选项，或者改选项的值为空，那么将会返回一个false。

通过get_option获得的值通常都可以在后台的"菜单"->"常规"中获得。而且它们内容如下：

admin_email   管理员的email地址

blogname      网站title标题

blogscription   网站描述

blog_charset   网站编码，一般都是utf-8

date_format    日期格式

default_category    文章默认分类

home         网站地址

siteurl       WordPress的web地址

template      当前主题名称

start_of-week    星期开始设置

upload_path      上传默认目录

posts_per_page   文章分页每页显示的数量

posts_per_rss     rss聚合显示的最新文章数量

需要注意的是该函数可以接受两个参数，如果查询的第一个参数不存在时，就会返回第二个参数。

如果只写一个参数，那么当查询的第一个参数不存在时，将会返回false。

get-option（）位于wp-includes/option.php文件中，其函数的源代码部分（3.9版本）如下：

/**
 * Option API
 *
 * @package WordPress
 * @subpackage Option
 */

/**
 * Retrieve option value based on name of option.
 *
 * If the option does not exist or does not have a value, then the return value
 * will be false. This is useful to check whether you need to install an option
 * and is commonly used during installation of plugin options and to test
 * whether upgrading is required.
 *
 * If the option was serialized then it will be unserialized when it is returned.
 *
 * @since 1.5.0
 *
 * @param string $option Name of option to retrieve. Expected to not be SQL-escaped.
 * @param mixed $default Optional. Default value to return if the option does not exist.
 * @return mixed Value set for the option.
 */
function get_option( $option, $default = false ) {
	global $wpdb;

	$option = trim( $option );
	if ( empty( $option ) )
		return false;

	/**
	 * Filter the value of an existing option before it is retrieved.
	 *
	 * The dynamic portion of the hook name, $option, refers to the option name.
	 *
	 * Passing a truthy value to the filter will short-circuit retrieving
	 * the option value, returning the passed value instead.
	 *
	 * @since 1.5.0
	 *
	 * @param bool|mixed $pre_option Value to return instead of the option value.
	 *                               Default false to skip it.
	 */
	$pre = apply_filters( 'pre_option_' . $option, false );
	if ( false !== $pre )
		return $pre;

	if ( defined( 'WP_SETUP_CONFIG' ) )
		return false;

	if ( ! defined( 'WP_INSTALLING' ) ) {
		// prevent non-existent options from triggering multiple queries
		$notoptions = wp_cache_get( 'notoptions', 'options' );
		if ( isset( $notoptions[$option] ) )

			/**
			 * Filter the default value for an option.
			 *
			 * The dynamic portion of the hook name, $option, refers
			 * to the option name.
			 *
			 * @since 3.4.0
			 *
			 * @param mixed $default The default value to return if the option
			 *                       does not exist in the database.
			 */
			return apply_filters( 'default_option_' . $option, $default );

		$alloptions = wp_load_alloptions();

		if ( isset( $alloptions[$option] ) ) {
			$value = $alloptions[$option];
		} else {
			$value = wp_cache_get( $option, 'options' );

			if ( false === $value ) {
				$row = $wpdb->get_row( $wpdb->prepare( "SELECT option_value FROM $wpdb->options WHERE option_name = %s LIMIT 1", $option ) );

				// Has to be get_row instead of get_var because of funkiness with 0, false, null values
				if ( is_object( $row ) ) {
					$value = $row->option_value;
					wp_cache_add( $option, $value, 'options' );
				} else { // option does not exist, so we must cache its non-existence
					$notoptions[$option] = true;
					wp_cache_set( 'notoptions', $notoptions, 'options' );

					/** This filter is documented in wp-includes/option.php */
					return apply_filters( 'default_option_' . $option, $default );
				}
			}
		}
	} else {
		$suppress = $wpdb->suppress_errors();
		$row = $wpdb->get_row( $wpdb->prepare( "SELECT option_value FROM $wpdb->options WHERE option_name = %s LIMIT 1", $option ) );
		$wpdb->suppress_errors( $suppress );
		if ( is_object( $row ) ) {
			$value = $row->option_value;
		} else {
			/** This filter is documented in wp-includes/option.php */
			return apply_filters( 'default_option_' . $option, $default );
		}
	}

	// If home is not set use siteurl.
	if ( 'home' == $option && '' == $value )
		return get_option( 'siteurl' );

	if ( in_array( $option, array('siteurl', 'home', 'category_base', 'tag_base') ) )
		$value = untrailingslashit( $value );

	/**
	 * Filter the value of an existing option.
	 *
	 * The dynamic portion of the hook name, $option, refers to the option name.
	 *
	 * @since 1.5.0 As 'option_' . $setting
	 * @since 3.0.0
	 *
	 * @param mixed $value Value of the option. If stored serialized, it will be
	 *                     unserialized prior to being returned.
	 */
	return apply_filters( 'option_' . $option, maybe_unserialize( $value ) );
}