Custom field fails with 503 error

Development Discussion
1

256 foreach ($custom_values as $custom_value) {
257 $field->$field_id_fieldlabel = $custom_value->custom_values_value;
.
… // Add as serialized string
. $field->$key_serialized .= $custom_value->custom_values_value;
. $field->$key_serialized .= $custom_value === end($custom_values) ? ‘’ : ', ';
262 }
263 }

Error LOG
[05-Oct-2017 17:30:19 Etc/GMT] PHP Fatal error: Cannot use for reading in
application/modules/custom_fields/models/Mdl_custom_fields.php on line 257application/modules/custom_fields/models/Mdl_custom_fields.php on line 257

2

Okk fixed Iam sorry

3

Relpaced 256 line with
array_push($field->$field_id_fieldlabel, $custom_value->custom_values_value);

4

Had the exact same issue and fixed it the same way ! Iam running a quite outdated WAMP with PHP 5.6.31, so its satisfying the requirement for invoiceplane.
I am just not 100% sure if the latest versions of invoiceplane are still getting tested with this version.