Description:
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The documentation doesn't mention that the 3rd parameter only works with php 5.3+



Test script:
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<?php
echo round(9.5, 0, PHP_ROUND_HALF_UP); 


Expected result:
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10

Actual result:
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Notice: Use of undefined constant PHP_ROUND_HALF_UP - assumed 'PHP_ROUND_HALF_UP' in test.php on line 2

Warning: Wrong parameter count for round() in test.php on line 2