Description:
------------
As of PHP 5.4, $_SERVER['REQUEST_TIME'] is no longer an int, but a float.
However, using Apache 2 SAPI, this server variable only have 3 decimal digits. 
This make DateTime::__construct() throw an exception :

Fatal error: Uncaught exception 'Exception' with message 
'DateTime::__construct(): Failed to parse time string (@1324314320.916) at 
position 12 (9): Unexpected character' in /Users/lolautruche/workspace/test.php 
on line 3

As a comparison, FPM and built-in server defines 4 decimal digits, which is 
valid.

This might affect Apache 1 SAPI as well.
This also might be related to #55733

Test script:
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<?php
var_dump( $_SERVER['REQUEST_TIME'] ); // Displays a float with 3 decimal digits with Apache2, 4 with FPM/built-in server
$date = new DateTime( '@' . $_SERVER['REQUEST_TIME'] );
var_dump( $date );

Expected result:
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$_SERVER['REQUEST_TIME'] should always have 4 decimal digits.