$isac_start = microtime(true);
function ilog($m) use ($isac_start){
$time_elapsed_secs = microtime(true) - $isac_start;
file_put_contents(__DIR__.'/debug_log.txt', $m . " - time elapsed: " . $time_elapsed_secs . "\n", FILE_APPEND | LOCK_EX);
}
gives me
undefined variable $isac_start
;
why? how to fix it?