Array to string conversion error using php v7.0.13 - php

Question

I have the following code in my laravel controller file.
$j_decode->$data['_kfdTourDate']->available = ($j_decode->$data['_kfdTourDate']->available+$totalincrement);
and I am getting the following error.
ErrorException in BookingsController.php line 325: Array to string
conversion in BookingsController.php line 325 at
HandleExceptions->handleError('8', 'Array to string conversion',
'D:\XAMPP\htdocs\lara\app\Http\Controllers\BookingsController.php',
'325', array('request' => object(Request), 'id' => '0', 'rules' =>
array(), 'validator' => object(Validator), 'data' => array('_kpnID' =>
'153290', '_kfnTourID' => '2', '_kfdTourDate' => '2017-03-16',
'nAdults' => '2', 'nChildren' => '1', 'nInfants' => '0', 'nBabies' =>
'2', 'nFOC' => '2', 'nPriceAdult' => '74.25', 'nPriceChild' => '49.5',
'nPriceInfant' => '0', 'nPriceBaby' => '0', 'nTotalPrice' => '148.5',
'tGuestName' => 'Yuhiko Nishioka', 'tGuestOrigin' => 'Unknown',
'tEnquirySourceWhat' => 'Unknown', 'tStatus' => 'Confirmed',
'_kfnAgentID' => '0', '_kfnPersonID' => '0', '_kfnInvoiceID' => '0',
'nAgentCommissionPercent' => '0', 'nDiscount_percent' => '0',
'nDiscount_fixed' => '0', 'tNotes' => '4WD Tour package/Rezdy, applied
discount', 'tInitials' => 'JD', 'CreatedOn' => '2017-01-21 15:08:00',
'ModifiedOn' => '2017-01-21 15:10:00', 'tTicketNumber' => 'Rezdy',
'_kfnOrganisationID' => '0'), 'schedule' => object(Collection),
'j_decode' => object(stdClass), 'update_id_data' => object(stdClass),
'totalincrement' => '3')) in BookingsController.php line 325
Interesting part that it's working on the linux server when I upload it to my host. I have PHP Version 7.0.13 on localhost and PHP Version 5.6.30 on the server.
How can this line cause an Array to string conversion error?
I am not willing to downgrade my php version on localhost as I have other codes that php5 is not supporting.
The whole code in controller:
$rules = $this->validateForm();
$validator = Validator::make($request->all(), $rules);
if ($validator->passes()) {
$data = $this->validatePost( $request );
$schedule = DB::table('schedule')
->where('id','=',$data['_kfnTourID'])
->get();
if(isset($_SESSION['bookingiddata']))
{
print_r ($j_decode= json_decode($schedule[0]->data));
$update_id_data = json_decode($_SESSION['bookingiddata']);
$totalincrement = $update_id_data->nAdults+$update_id_data->nChildren+$update_id_data->nInfants+$update_id_data->nFOC;
//$j_decode->$data['_kfdTourDate']->available = ($j_decode->$data['_kfdTourDate']->available+$totalincrement);
$j_decode->$data['_kfdTourDate']['available'] = ($j_decode->$data['_kfdTourDate']['available']+$totalincrement);
($j_decode->$data)['_kfdTourDate']->status = "available";
Also print_r $j_encode = json_encode($j_decode); prints me the following
{"2017-02-13":{"available":1,"bind":0,"info":"","notes":"","price":0,"promo":0,"status":"available"},"2017-02-14":{"available":1,"bind":0,"info":"","notes":"","price":0,"promo":0,"status":"available"},"2017-02-08":{"available":0,"bind":0,"info":"","notes":"","price":0,"promo":0,"status":"booked"},"2017-02-12":{"available":0,"bind":0,"info":"","notes":"","price":0,"promo":0,"status":"booked"},"2017-02-10":{"available":0,"bind":0,"info":"","notes":"","price":0,"promo":0,"status":"booked"},"2017-02-15":{"available":0,"bind":0,"info":"","notes":"","price":0,"promo":0,"status":"booked"},"2017-02-16":{"available":0,"bind":0,"info":"","notes":"","price":0,"promo":0,"status":"booked"}...

Answer 1

well, as mentioned here
in php 5.6.3 , it's allowed to use this expression:
echo $json_decode->$data['_kfdTourDate']->available;
so , you are trying to access the value of $data['_kfdTourDate'] which is element in $json_decode object
for example: https://3v4l.org/i9Q7p
in php 7,
Indirect access to variables, properties, and methods will now be
evaluated strictly in left-to-right order, as opposed to the previous
mix of special cases. The table below shows how the order of
evaluation has changed.
so, the interpreter will interpret this code as follow:
echo $json_decode->$data['_kfdTourDate']->available;
// first , give me the value $json_decode->$data,
// then choose the _kfdTourDate key
and to solve this, you need to :
echo $json_decode->{$data['_kfdTourDate']}->available;
to tell php that $data['_kfdTourDate'] is just a value;

Answer 2

There were some order-of-operations changes in PHP7 (see Changes to the handling of indirect variables, properties, and methods). I suspect you might need to mess around with some parentheses within $j_decode->$data['_kfdTourDate']->available to make it evaluate in the order you want.