Description:
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When running sleep(), I noticed it does not always pause the script for the exact amount of time.  Although the difference is no doubt neglectible, it is still noteable.

Reproduce code:
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<?php $st = array_sum (explode (' ', microtime ()));

sleep (1);

echo round ((array_sum (explode (' ',microtime ())) - $st), 7); ?>

Expected result:
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I expect to see values ranging around 1.0000001 to 1.01 (depending on lag).

Actual result:
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It returned the following: (including server lag)

0.9998388
0.9999161
1.001672