note 57413 added to function.eval

see: http://us2.php.net/manual/en/function.eval.php#51766 This nice suggestion about eval speed below made me curious about some code I have been using as a shortcut, so I came up with a qad test to see what the difference between inline and eval code might be with loops. <?php /* The test code basically adds and subtracts 1 from $ref $n times. */ // straight PHP function control($n) { $ref = 0; while ($n-- > 0) { $ref += ($n % 2) ? 1 : -1; } return $ref; } // eval with return function testEval($n) { $ref = 0; while ($n-- > 0) { $ref += eval('return ($n % 2) ? 1 : -1;'); } return $ref; } // eval with inline scalar assignment function testEval1($n) { $ref = 0; while ($n-- > 0) { eval('$ref += ($n % 2) ? 1 : -1;'); } return $ref; } // eval with while loop inlined function testEval2($n) { $ref = 0; eval('while ($n-- > 0) { $ref += ($n % 2) ? 1 : -1; }'); return $ref; } // PHP4 hack to get a number from microtime() function microseconds() { $microString = microtime(); $microArray = split(' ',$microString); $microSeconds = doubleval($microArray[0]) + (intval($microArray[1]) % 1000); return $microSeconds; } echo '<pre>'; // on a Pentium M 1.5GHz laptop--adjust at will $n = 100000; $t = array(); // timers $t[] = microseconds(); control($n); $t[] = microseconds(); testEval($n); $t[] = microseconds(); testEval1($n); $t[] = microseconds(); testEval2($n); $t[] = microseconds(); $base = 0; foreach ($t as $ti) { echo ($ti - $base).'<br />'; $base = $ti; } echo '</pre>'; ?> returns: 200.543225 // base time (modulo 1000 seconds) 0.081147 // time for control (straight PHP loop) -- control() 1.636144 // time for 'return from eval' -- testEval() 1.816688 // time for 'in eval assignment' -- testEval1() 0.079999 // time for 'loop inlined eval' -- testEval2() Interestingly, and maybe temptingly, the eval'd loop performs slightly faster than the normal PHP loop. This relationship is consistent across several runs. I'd be interested to know what features of the interpreter lead to faster execution here. Perhaps recursive eval calls would lead to the Holy Grail of 'zero execution time'. Note also: Returns from eval are slightly faster than in-eval assignments. ---- Manual Page -- http://www.php.net/manual/en/function.eval.php Edit -- http://master.php.net/manage/user-notes.php?action=edit+57413 Delete: added to the manual -- http://master.php.net/manage/user-notes.php?action=delete+57413&report=yes&reason=added+to+the+manual Delete: bad code -- http://master.php.net/manage/user-notes.php?action=delete+57413&report=yes&reason=bad+code Delete: spam -- http://master.php.net/manage/user-notes.php?action=delete+57413&report=yes&reason=spam Delete: useless -- http://master.php.net/manage/user-notes.php?action=delete+57413&report=yes&reason=useless Delete: non-english -- http://master.php.net/manage/user-notes.php?action=delete+57413&report=yes&reason=non-english Delete: already in docs -- http://master.php.net/manage/user-notes.php?action=delete+57413&report=yes&reason=already+in+docs Delete: other reasons -- http://master.php.net/manage/user-notes.php?action=delete+57413&report=yes Reject -- http://master.php.net/manage/user-notes.php?action=reject+57413&report=yes Search -- http://master.php.net/manage/user-notes.php