如何使用PHP获取和存储webview cookie？

Question

I'm making my first app, and i want to enable PHP cookies and use them after app is reopened, so far after some hours of googeling, none result

I tried some codes from other StackOverflow posts, so far i haven't got any result what so ever

public class MainActivity extends AppCompatActivity {
    private WebView homepage;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        homepage = (WebView)findViewById(R.id.webviewid);
        homepage.setWebViewClient(new WebViewClient());
        homepage.loadUrl("MyWebSiteUrl");
        homepage.getSettings().setSupportMultipleWindows(true);
        homepage.getSettings().setJavaScriptCanOpenWindowsAutomatically(true);
        homepage.setWebChromeClient(new WebChromeClient());
        homepage.getSettings().setDomStorageEnabled(true);
        homepage.getSettings().setAllowFileAccess(true);
        homepage.getSettings().setAllowFileAccessFromFileURLs(true);
        homepage.getSettings().setAppCacheEnabled(true);
        homepage.getSettings().setJavaScriptEnabled(true);
        homepage.getSettings().setCacheMode(WebSettings.LOAD_CACHE_ELSE_NETWORK);
    }
    public String getCookie(String homepage,String CookieName){
        String CookieValue = null;

        CookieManager cookieManager = CookieManager.getInstance();
        String cookies = cookieManager.getCookie(homepage);
        if(cookies != null){
            String[] temp=cookies.split(";");
            for (String ar1 : temp ){
                if(ar1.contains(CookieName)){
                    String[] temp1=ar1.split("=");
                    CookieValue = temp1[1];
                }
            }
        }
        return CookieValue;
    }

}

I'm using some basic php codes to check if cookies are set

    if(isset($_COOKIE['username'] ) and ($_COOKIE['password'] )){
        echo "Cookies are set";
        echo $_COOKIE['username'];
        echo "<p>", $_COOKIE['password'];
        user_login(($_COOKIE['username'] ),($_COOKIE['password'] ));
    }else{
        echo "<p>Cookies are not set";
    }

I tried also some code lines from developer.android, 0 results from there also, I'm not sure even, if I have problems inside app or in my back-end PHP