Description:
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$_SERVER['REQUEST_TIME'] is a very nice feature, But since many scripts runs in less than 0.1 seconds, would be nice exists a $_SERVER['STARTUP_MICRO_TIME'], so would be possible do something like below:

Reproduce code:
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<?
$times['startup'] = $_SERVER['STARTUP_MICRO_TIME']

require_once 'any.php';

$times['require'] = microtime(true);

... // more code

$times['more_code'] = microtime(true);

printTimes($times);

function printTimes($times) {
... // use $_SERVER['REQUEST_MICRO_TIME']
}

?>

Expected result:
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A fine grained time elapse calculation

Actual result:
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not perfect time elapse calculation