2010/1/27 Richard Quadling <rquadling@xxxxxxxxxxxxxx>: > 2010/1/27 Michael A. Peters <mpeters@xxxxxxx>: >> Paul M Foster wrote: >>> >>> "... should be obvious - but are often overlooked - points within coding >>> practice that can cause the programmer to develop bad habits and bad >>> code." - Dan Brown >>> >>> Tip #1: >>> >>> Don't use count() in loops unless there are very few items to count and >>> performance doesn't matter, or the number will vary over the loop. That >>> is, don't do this: >>> >>> for ($i = 0; $i < count($items); $i++) >>> >>> Instead, do this: >>> >>> $number = count($items); >>> for ($i = 0; $i < $number; $i++) >> >> Gah! >> >> for ($i=0;$i<sizeof($array);$i++) >> >> is something I do all the time. >> So the array size is being calculated each iteration? >> >> -- >> PHP General Mailing List (http://www.php.net/) >> To unsubscribe, visit: http://www.php.net/unsub.php >> >> > > for ($i = 0, $j = count($a) ; $i < $j ; ++$i) { > } > > is a very common way to handle that. > > Of course... > > foreach(range(0, count($a)) as $i) { > } > > is an alternative. > > You can see the effect of the counting if you replace ... > > count($a) > > with ... > > mycount($a) > > and have ... > > function mycount($a) { > echo 'Counting : ', count($a), PHP_EOL; > return count($a); > } <?php function mycount($a) { echo 'Counting : ', count($a), PHP_EOL; return count($a); } $a = array(1,2,3,4,5,6,7,8,9,10); echo PHP_EOL; for($i = 0 ; $i < mycount($a) ; ++$i) { echo 'Traditional for() loop ', $i, PHP_EOL; } echo PHP_EOL; for($i = 0, $j = mycount($a) ; $i < $j ; ++$i) { echo 'Modern for() loop ', $i, PHP_EOL; } echo PHP_EOL; foreach(range(0, mycount($a)) as $i) { echo 'Ultra-modern foreach() with range() loop ', $i, PHP_EOL; } ?> outputs ... Counting : 10 Traditional for() loop 0 Counting : 10 Traditional for() loop 1 Counting : 10 Traditional for() loop 2 Counting : 10 Traditional for() loop 3 Counting : 10 Traditional for() loop 4 Counting : 10 Traditional for() loop 5 Counting : 10 Traditional for() loop 6 Counting : 10 Traditional for() loop 7 Counting : 10 Traditional for() loop 8 Counting : 10 Traditional for() loop 9 Counting : 10 Counting : 10 Modern for() loop 0 Modern for() loop 1 Modern for() loop 2 Modern for() loop 3 Modern for() loop 4 Modern for() loop 5 Modern for() loop 6 Modern for() loop 7 Modern for() loop 8 Modern for() loop 9 Counting : 10 Ultra-modern foreach() with range() loop 0 Ultra-modern foreach() with range() loop 1 Ultra-modern foreach() with range() loop 2 Ultra-modern foreach() with range() loop 3 Ultra-modern foreach() with range() loop 4 Ultra-modern foreach() with range() loop 5 Ultra-modern foreach() with range() loop 6 Ultra-modern foreach() with range() loop 7 Ultra-modern foreach() with range() loop 8 Ultra-modern foreach() with range() loop 9 Ultra-modern foreach() with range() loop 10 So, with the count inline, there are actually 11 calls to the count compared to 1 in each of the other 2 scenarios. -- ----- Richard Quadling "Standing on the shoulders of some very clever giants!" EE : http://www.experts-exchange.com/M_248814.html EE4Free : http://www.experts-exchange.com/becomeAnExpert.jsp Zend Certified Engineer : http://zend.com/zce.php?c=ZEND002498&r=213474731 ZOPA : http://uk.zopa.com/member/RQuadling -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
