Fine JSON errors in JSONL file

parse-json.php

<?php

$fin = fopen($argv[1], 'r');
$lno = 0;
while ($line = fgets($fin)) {
        $lno++;
        try {
                $decoded = json_decode($line, true, 512);
                if ($decoded === null && json_last_error() !== JSON_ERROR_NONE) {
                        throw new \Exception("Invalid JSON format");
                }
        } catch (Exception $e) {
                if (json_last_error() !== JSON_ERROR_NONE) {
                        echo "JSON error on line $lno: " . json_last_error_msg() . "\n";
                } else {
                        echo "Unknown error on line $lno\n";
                }
        }
}
echo "parsed $lno lines\n";