public function addAlternateUrl(string $locale, string $url): void
    {
        $this->alternateUrl[$locale] = $url;
    }
public function addAlternateUrl(string $locale, string $url): void
    {
        $this->alternateUrl[$locale] = $url;
    }
public function addAlternateUrl ( string $ locale , string $ url ) : void { $ this -> alternateUrl [ $ locale ] = $ url ; }
Add an alternate url to the current one.

If you have multiple language versions of a URL, each language page in
the set must use rel="alternate" hreflang="x" to identify all language
versions including itself. For example, if your site provides content
in French, English, and Spanish, the Spanish version must include a
rel="alternate" hreflang="x" link for itself in addition to links to the
French and English versions. Similarly the English and French versions
must each include the same references to the French, English, and
Spanish versions.

@param string $locale The url's language (and optionnaly region. Ex: en, en-us).
Add an alternate url to the current one .