For that, you need to move your web app to the shared/standard mode and:
1) configure url rewriting (like described here)
2) configure multiple domain names using Site.HostNames property. That property can be used for setting additional domains. Unfortunately, i have no PHP code snippet, but working C# code is below (implemented using SDK). And, again, unfortunately, but it looks like the official Azure PHP SDK does not provide the same functionality. The way here would be to write a REST API wrapper using, for example, the snippet below as a reference. If there is no possibility from your side to execute the code and catch the request, i can do that a little later, if that will help.
public const string base64EncodedCertificate = "ManagementCertificateValueFromPublishSettingsFile";
public const string subscriptionId = "AzureSubscriptionId";
static SubscriptionCloudCredentials getCredentials()
{
return new CertificateCloudCredentials(subscriptionId, new X509Certificate2(Convert.FromBase64String(base64EncodedCertificate)));
}
static void Main(string[] args)
{
WebSiteManagementClient client = new WebSiteManagementClient(getCredentials());
WebSpacesListResponse n = client.WebSpaces.List();
n.Select(p =>
{
Console.WriteLine("webspace {0}", p.Name);
WebSpacesListWebSitesResponse websitesInWebspace = client.WebSpaces.ListWebSites(p.Name,
new WebSiteListParameters()
{
});
websitesInWebspace.Select(o =>
{
Console.Write(o.Name);
return o;
}).ToArray();
return p;
}).ToArray();
Console.ReadLine();
var configuration = client.WebSites.Get("WebSpaceName", "WebSiteName", new WebSiteGetParameters());
configuration.WebSite.HostNames.Add("new domain");
var resp = client.WebSites.Update("WebSpaceName", "WebSiteName", new WebSiteUpdateParameters() { HostNames = configuration.WebSite.HostNames });
Console.WriteLine(resp.StatusCode);
Console.ReadLine();
}