Description:
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rounding function not as expected

Test script:
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#  tested PHP 5.2, 5.3, 5.4, 5.5, 5.6, 7.0, 7.2.12
for( $i = 0; $i < 100; $i += 0.001 ) {
	$r_0	= round( $i );
	$r_up	= round( $i, 2, PHP_ROUND_HALF_UP );
	$r_down	= round( $i, 2, PHP_ROUND_HALF_DOWN );
	# a) missing values 
	#	Line  7- 8:  0,085 +  0,095
	#	Line 73-74:  0,765 -  0,995
	#	Line 78-79:  1,055 -  4,965
	#	Line 81-82:  5,005 -  9,795
	#	Line 83-84:  9,825 - 18,755
	#	Line 92-93: 18,855 - 38,885
	#	Line 97-98: 38,945 - 76,225
	#	Line 101+ : 76,235 - 99,995
	if( $r_up == $r_down ) continue; // comment out... -> attention! producing 99.999 lines
	#	see lines: 1.461 - 4.836, 5.137 - 9.723, 9.905 - 10.000, 10.717 - 18.396,
	#	19.215 - 38.703, 39.133 - 76.139, 76.349 - 99.999
	echo 'Line ' . $count++ . "| {$i} | round 0: {$r_0} | half up: {$r_up} | half down: {$r_down} <br>";
}