尝试将html字符串转换为JSONObject时发生JSONException

我知道很多人都遇到同样的问题，但是任何答案都可以帮助我。所有人都把我弄糊涂了。
我正在尝试在Android上进行登录/注册。问题显示如下。

W/System.err: org.json.JSONException: Value <br><table of type java.lang.String cannot be converted to JSONObject 
W/System.err:     at org.json.JSON.typeMismatch(JSON.java:111)
W/System.err:     at org.json.JSONObject.<init>(JSONObject.java:160)
W/System.err:     at org.json.JSONObject.<init>(JSONObject.java:173)
...

这是我的代码。

final Button bRegister = (Button) findViewById(R.id.rButton);

    bRegister.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            final String name = etName.getText().toString();
            final String username = etUsername.getText().toString();
            final String password = etPassword.getText().toString();

            Response.Listener<String> responseListener = new Response.Listener<String>() {
                @Override
                public void onResponse(String response) {
                    try {
                        JSONObject jsonResponse = new JSONObject(response);
                        boolean success = jsonResponse.getBoolean("success");
                        if (success) {
                            Intent intent = new Intent(RegisterActivity.this, LoginActivity.class);
                            RegisterActivity.this.startActivity(intent);
                        } else {
                            AlertDialog.Builder builder = new AlertDialog.Builder(RegisterActivity.this);
                            builder.setMessage("Register Failed")
                                    .setNegativeButton("Retry", null)
                                    .create()
                                    .show();
                        }
                    } catch (JSONException e) {
                        e.printStackTrace();
                    }
                }
            };

            RegisterRequest registerRequest = new RegisterRequest(name, username, password, responseListener);
            RequestQueue queue = Volley.newRequestQueue(RegisterActivity.this);
            queue.add(registerRequest);
        }
    });
}

}

当然是php之一。

<?php
$con = mysqli_connect("host", "user", "password", "database");


$name = $_POST["name"];
$username = $_POST["username"];
$password = $_POST["password"];
$statement = mysqli_prepare($con, "INSERT INTO user (name, username, password) VALUES (?, ?, ?)");
mysqli_stmt_bind_param($statement, "sss", $name, $username, $password);
mysqli_stmt_execute($statement);

$response = array();
$response["success"] = true;  

echo json_encode($response); 

在此先感谢您的帮助，对于造成的麻烦我们深表歉意。