basically, as I understand it, PHP 7 lets you do something like this
// create a value that is a string
$value = 'ABCD';
// use the above variable and replace it with an array
// this automatically unsets the variable and creates an array
$value[] = 'ABCD'
PHP 8 does not allow this. You would first need to reinitialize the variable to an array
// set a variable with a string value
$value = 'ABCD';
// set the var to an array
$value = array();
// set at array var
$value[] = 'ABCD'
