Yield

function csvFileGenerator($csv_file_path) {
    try {
        $csv_file = fopen($csv_file_path, 'r');
        $csv_headers = fgetcsv($csv_file);
        while ($csv_line = fgetcsv($csv_file)) {
            $csv_data_with_key = array_combine($csv_headers, $csv_line);
            yield $csv_data_with_key;
        }
    } finally {
        fclose($csv_file);
    }
}

$csv_file_path = '/var/my/csv/path.csv';
foreach(csvFileGenerator($csv_file_path) as $csv_data_with_key) {
    // process csv data with key
}