get_term_by( string $field, string|int $value, string $taxonomy = ”, string $output = OBJECT, string $filter = ‘raw’ )

按术语字段和数据从数据库中获取所有术语数据。
Get all Term data from database by Term field and data.

目录锚点：#说明#参数#返回#源码#笔记

说明（Description）

另见函数 sanitize_term_field()

参数（Parameters）

返回（Return）

（WP|Term|array|false）WP_Term实例（WP|Term|array|false）成功时。如果$taxonomy不存在或找不到$term，则返回false。

源码（Source）

/**
 * Get all Term data from database by Term field and data.
 *
 * Warning: $value is not escaped for 'name' $field. You must do it yourself, if
 * required.
 *
 * The default $field is 'id', therefore it is possible to also use null for
 * field, but not recommended that you do so.
 *
 * If $value does not exist, the return value will be false. If $taxonomy exists
 * and $field and $value combinations exist, the Term will be returned.
 *
 * @todo Better formatting for DocBlock.
 *
 * @since 2.3.0
 *
 * @global wpdb $wpdb WordPress database abstraction object.
 * @see sanitize_term_field() The $context param lists the available values for get_term_by() $filter param.
 *
 * @param string     $field    Either 'slug', 'name', 'id' (term_id), or 'term_taxonomy_id'
 * @param string|int $value    Search for this term value
 * @param string     $taxonomy Taxonomy Name
 * @param string     $output   Constant OBJECT, ARRAY_A, or ARRAY_N
 * @param string     $filter   Optional, default is raw or no WordPress defined filter will applied.
 * @return object|array|null|WP_Error|false Term Row from database.
 *                                          Will return false if $taxonomy does not exist or $term was not found.
 */
function get_term_by($field, $value, $taxonomy, $output = OBJECT, $filter = 'raw') {
	global $wpdb;

	if ( ! taxonomy_exists($taxonomy) )
		return false;

	if ( 'slug' == $field ) {
		$field = 't.slug';
		$value = sanitize_title($value);
		if ( empty($value) )
			return false;
	} elseif ( 'name' == $field ) {
		// Assume already escaped
		$value = wp_unslash($value);
		$field = 't.name';
	} elseif ( 'term_taxonomy_id' == $field ) {
		$value = (int) $value;
		$field = 'tt.term_taxonomy_id';
	} else {
		$term = get_term( (int) $value, $taxonomy, $output, $filter );
		if ( is_wp_error( $term ) )
			$term = false;
		return $term;
	}

	$term = $wpdb->get_row( $wpdb->prepare( "SELECT t.*, tt.* FROM $wpdb->terms AS t INNER JOIN $wpdb->term_taxonomy AS tt ON t.term_id = tt.term_id WHERE tt.taxonomy = %s AND $field = %s LIMIT 1", $taxonomy, $value ) );
	if ( ! $term )
		return false;

	wp_cache_add( $term->term_id, $term, $taxonomy );

	/** This filter is documented in wp-includes/taxonomy.php */
	$term = apply_filters( 'get_term', $term, $taxonomy );

	/** This filter is documented in wp-includes/taxonomy.php */
	$term = apply_filters( "get_$taxonomy", $term, $taxonomy );

	$term = sanitize_term($term, $taxonomy, $filter);

	if ( $output == OBJECT ) {
		return $term;
	} elseif ( $output == ARRAY_A ) {
		return get_object_vars($term);
	} elseif ( $output == ARRAY_N ) {
		return array_values(get_object_vars($term));
	} else {
		return $term;
	}
}

笔记（Notes）

get_term_by（）返回单个WP_term对象。由于核心版本从v4.1到4.3的变化，现在可以使用多个术语来匹配提供的名称或slug参数。返回的WP_Term对象将是mySQL找到的第一个匹配项，没有迹象表明可能存在其他匹配项。如果应用程序中可能有多个具有相同名称或slug的术语，则应使用get_terms（）而不是get_term_by（）。
按类别名称检索类别的示例：
实例