Fatal error of echo a date variable that allow nulls

I'm trying to fill a HTML table with the different values of a table in SQL Server working with PHP. This is the code.

...
while($datosPerfil = sqlsrv_fetch_array($resultado)){
            echo "<tr>";
            echo "<td>";
            echo $datosPerfil['CPR_Name'];
            echo "</td>";
            echo "<td>";
            echo $datosPerfil['CON_SC_Id'];
            echo "</td>";
            echo "<td>";
            echo $datosPerfil['CON_Tel_Number'];
            echo "</td>";
            echo "<td>";
            echo $datosPerfil['CON_Startup_Date'];
            echo "</td>";
            echo "</tr>";
}
....

The field "CON_Startup_Date" is date type and allow nulls. And this is the error that appears:

Catchable fatal error: Object of class DateTime could not be converted to string

And when I write:

echo $datosPerfil['CON_Startup_Date']->format("Y-m-d");

It works but when arrives to a null value shows an error:

Fatal error: Call to a member function format() on null

Any solution that allows to run the echo for null values and correctly in date type?