This is now illegal if $a is not initialized at each level.
$a["a"]["b"]["c"] +=1;
Does exists a syntax to force php8.2 to behave like php5.6 and so auto-initialize the $a["a"]["b"]["c"] to value zero, if and only if not already defined to each level?
You can use the Null coalescing operator ?? (as of PHP 7.0), to use 0 is any element of the chain is not defined.
Example:
$a['a']['b']['c'] = ($a['a']['b']['c'] ?? 0) + 1;
echo json_encode($a), PHP_EOL; // a.b.c = 1
$a['a']['b']['c'] = ($a['a']['b']['c'] ?? 0) + 1;
echo json_encode($a), PHP_EOL; // a.b.c = 2
Output:
{"a":{"b":{"c":1}}}
{"a":{"b":{"c":2}}}