I have a simple form that submits a name to a database. the php works on the html form already.
xml for form

<Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button"
        android:onClick="sumbitdata"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        tools:layout_constraintTop_creator="1"
        tools:layout_constraintRight_creator="1"
        android:layout_marginTop="53dp"
        app:layout_constraintTop_toBottomOf="@+id/name"
        tools:layout_constraintLeft_creator="1" />

    <EditText
        android:id="@+id/name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:ems="10"
        android:inputType="textPersonName"
        android:text="Name"
        tools:layout_constraintTop_creator="1"
        tools:layout_constraintRight_creator="1"
        android:layout_marginEnd="69dp"
        app:layout_constraintRight_toRightOf="parent"
        android:layout_marginTop="222dp"
        app:layout_constraintTop_toTopOf="parent"
        android:layout_marginRight="69dp" />
</android.support.constraint.ConstraintLayout>

java for from page

public class checklist extends AppCompatActivity {
EditText name;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_checklist);
        name = (EditText)findViewById(R.id.name);

    }

    public void poslji (View view){

        String checklist_data = name.getText().toString().trim();
        String type ="mydata";
        backgroundworker backgroundWorker = new backgroundworker(this);
        backgroundWorker.execute(type, checklist_data);
    }

    }

background worker java

class backgroundworker extends AsyncTask<String,Void,String> {

    Context context;
    backgroundworker (Context ctx) {
        context=ctx;
    }
    @Override
    protected  String doInBackground (String... params){
        String type = params [0];
        String submit_url= "http://mylocalwebsever/submit.php";
        if(type.equals("mydata")) {
            try {
                String name = params[1];
                URL url = new URL( submit_url );
                HttpURLConnection httpURLConnection = (HttpURLConnection)
url.openConnection();
                httpURLConnection.setRequestMethod( "POST" );
                httpURLConnection.setDoOutput( true );
                httpURLConnection.setDoInput( true );
                OutputStream outputStream =
httpURLConnection.getOutputStream();
                BufferedWriter bufferedWriter = new BufferedWriter( new
OutputStreamWriter( outputStream, "UTF-8" ) );
                String post_data = URLEncoder.encode( "name", "UTF-8" ) +
"=" + URLEncoder.encode( name, "UTF-8");
                bufferedWriter.write( post_data );
                bufferedWriter.flush();
                bufferedWriter.close();
                InputStream inputStream = httpURLConnection.getInputStream
();
                BufferedReader bufferedReader = new BufferedReader( new
InputStreamReader( inputStream, "iso-8859-1" ) );
                String result = "";
                String line = "";
                while ((line = bufferedReader.readLine()) != null) {

                    result += line;
                }
                bufferedReader.close();
                inputStream.close();
                httpURLConnection.disconnect();
                return result;
            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return null;
    }