note 57281 added to language.operators.bitwise

note that the shift operators are arithmetic, not logic like in C. You may get unexpected results with negative numbers, see http://en.wikipedia.org/wiki/Bitwise_operation here's a function to do logic right shifts. <?php function lshiftright($var,$amt) { $mask = 0x40000000; if($var < 0) { $var &= 0x7FFFFFFF; $mask = $mask >> ($amt-1); return ($var >> $amt) | $mask; } return $var >> $amt; } $val = -10; printf("arithmetic shift on a negative integer<br>%1\$032b<br>%2\$032b<br>%1\$0d<br>%2\$0d<br>",$val, $val >> 1 ); printf("logic shift on a negative integer<br>%1\$032b<br>%2\$032b<br>%1\$0d<br>%2\$0d<br>",$val, lshiftright($val, 1)); printf("logic shift on a positive integer<br>%1\$032b<br>%2\$032b<br>%1\$0d<br>%2\$0d<br>",-$val, lshiftright(-$val, 1)); ?> gives the output: arithmetic shift on a negative integer 11111111111111111111111111110110 11111111111111111111111111111011 -10 -5 logic shift on a negative integer 11111111111111111111111111110110 01111111111111111111111111111011 -10 2147483643 logic shift on a positive integer 00000000000000000000000000001010 00000000000000000000000000000101 10 5 ---- Manual Page -- http://www.php.net/manual/en/language.operators.bitwise.php Edit -- http://master.php.net/manage/user-notes.php?action=edit+57281 Delete: added to the manual -- http://master.php.net/manage/user-notes.php?action=delete+57281&report=yes&reason=added+to+the+manual Delete: bad code -- http://master.php.net/manage/user-notes.php?action=delete+57281&report=yes&reason=bad+code Delete: spam -- http://master.php.net/manage/user-notes.php?action=delete+57281&report=yes&reason=spam Delete: useless -- http://master.php.net/manage/user-notes.php?action=delete+57281&report=yes&reason=useless Delete: non-english -- http://master.php.net/manage/user-notes.php?action=delete+57281&report=yes&reason=non-english Delete: already in docs -- http://master.php.net/manage/user-notes.php?action=delete+57281&report=yes&reason=already+in+docs Delete: other reasons -- http://master.php.net/manage/user-notes.php?action=delete+57281&report=yes Reject -- http://master.php.net/manage/user-notes.php?action=reject+57281&report=yes Search -- http://master.php.net/manage/user-notes.php