How to fix "Json Parse Error: Unexpected EOF" error sent in ReactNative?

Question

So i'm developing a ReactNative App, and to create a new user, i'm creating a Json with the informations given by the user, and i send it to a PhP file which Parse the Json received to store it in the Database. But the problem is that my JSON doesn't send, and i have this magnificent Red Screen "JSON Parse Error : Unexpected EOF" If you guys have a solution for me, that would be wonderful after long nights of debug ..

Here is my code for the Fetch :

   Insert_Data_Into_MySQL = () =>
{
    this.setState({ ActivityIndicator_Loading : true }, () =>
    {
        fetch('http://MyPathToMyServerButDontWorryItsAnExample/NewUser.php',
        {
            method: 'POST',
            headers: 
            {
                'Accept': 'application/json',
                'Content-Type': 'application/json'
            },
            body: JSON.stringify(
            {
              product_name : this.state.Product_Name,
              product_number : this.state.Product_Number,
              product_details : this.state.Product_Details
            })

        })
        .then((response) => response.json()).then((responseJsonFromServer) =>
        {
            Alert.alert(responseJsonFromServer);
            this.setState({ ActivityIndicator_Loading : false });
        }).catch((error) =>
        {
            console.error(error);
            this.setState({ ActivityIndicator_Loading : false});
        });
    });
}

Thank's a lot guys !