检索附件的URL。

原型

wp_get_attachment_url( int $attachment_id )

参数

$attachment_id (int) (Optional)  附件帖子ID。默认为全球$ post。

返回值

(string|false)  附件网址,否则为false。

源文件

路径:wp-includes/post.php

<?php
...
function wp_get_attachment_url( $attachment_id = 0 ) {
	$attachment_id = (int) $attachment_id;
	if ( ! $post = get_post( $attachment_id ) ) {
		return false;
	}
	if ( 'attachment' != $post->post_type )
		return false;
	$url = '';
	// Get attached file.
	if ( $file = get_post_meta( $post->ID, '_wp_attached_file', true ) ) {
		// Get upload directory.
		if ( ( $uploads = wp_get_upload_dir() ) && false === $uploads['error'] ) {
			// Check that the upload base exists in the file location.
			if ( 0 === strpos( $file, $uploads['basedir'] ) ) {
				// Replace file location with url location.
				$url = str_replace($uploads['basedir'], $uploads['baseurl'], $file);
			} elseif ( false !== strpos($file, 'wp-content/uploads') ) {
				// Get the directory name relative to the basedir (back compat for pre-2.7 uploads)
				$url = trailingslashit( $uploads['baseurl'] . '/' . _wp_get_attachment_relative_path( $file ) ) . basename( $file );
			} else {
				// It's a newly-uploaded file, therefore $file is relative to the basedir.
				$url = $uploads['baseurl'] . "/$file";
			}
		}
	}
	/*
	 * If any of the above options failed, Fallback on the GUID as used pre-2.7,
	 * not recommended to rely upon this.
	 */
	if ( empty($url) ) {
		$url = get_the_guid( $post->ID );
	}
	// On SSL front end, URLs should be HTTPS.
	if ( is_ssl() && ! is_admin() && 'wp-login.php' !== $GLOBALS['pagenow'] ) {
		$url = set_url_scheme( $url );
	}
	/**
	 * Filters the attachment URL.
	 *
	 * @since 2.1.0
	 *
	 * @param string $url           URL for the given attachment.
	 * @param int    $attachment_id Attachment post ID.
	 */
	$url = apply_filters( 'wp_get_attachment_url', $url, $post->ID );
	if ( empty( $url ) )
		return false;
	return $url;
}
...
?>

其他

英文文档:https://developer.wordpress.org/reference/functions/wp_get_attachment_url/