Retrieve a URL within the plugins or mu-plugins directory.

Defaults to the plugins directory URL if no arguments are supplied.

Signature

plugins_url( $path = '', $plugin = '' )
path
 (string) Optional. Extra path appended to the end of the URL, including the relative directory if $plugin is supplied. Default empty.
Default: ''
plugin
 (string) Optional. A full path to a file inside a plugin or mu-plugin. The URL will be relative to its directory. Default empty. Typically this is done by passing `__FILE__` as the argument.
Default: ''

Return

(string) Plugins URL link with optional paths appended.

Source

function plugins_url( $path = '', $plugin = '' ) {

	$path = wp_normalize_path( $path );
	$plugin = wp_normalize_path( $plugin );
	$mu_plugin_dir = wp_normalize_path( WPMU_PLUGIN_DIR );

	if ( !empty($plugin) && 0 === strpos($plugin, $mu_plugin_dir) )
		$url = WPMU_PLUGIN_URL;
	else
		$url = WP_PLUGIN_URL;


	$url = set_url_scheme( $url );

	if ( !empty($plugin) && is_string($plugin) ) {
		$folder = dirname(plugin_basename($plugin));
		if ( '.' != $folder )
			$url .= '/' . ltrim($folder, '/');
	}

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