On Thu, Jan 28, 2010 at 11:41:43AM -0000, Ford, Mike wrote: > > -----Original Message----- > > From: Rene Veerman [mailto:rene7705@xxxxxxxxx] > > Sent: 27 January 2010 22:46 > > > > And if your script needs to pass large (> 5Mb) arrays around to > > functions, be sure to use passing-by-reference; failing to do so can > > double your memory requirements, > > possibly hitting the ini_set('memory_lmit', ??) > > Have you benchmarked this? PHP's copy-on-change philosophy means there shouldn't be much difference in memory terms -- so unless you actually expect to change the array's contents, you should pass by value. > > As proof, I constructed this little test: <snip> > All in all, there is no evidence that passing arrays to functions by value is inherently more expensive than by reference, and in fact in some cases it can be significantly cheaper. Which in turn says that you should only pass arguments by reference when you actually expect to change them, which is after all what the by-reference operator is there for in the first place! QED. > Counter-intuitive benchmarks. Can we not? Benchmarking something on a given version of PHP is nice, but changes to the PHP engine occur on a relatively routine basis. Shall we benchmark each "tip" each time we change PHP versions, and then rework all our code to conform to the latest benchmark, depending on the version of PHP our code is running under? A better example might be the use of single, versus double quotes. Regardless of benchmarks, it's logically obvious that if the PHP engine doesn't have to evaluate the contents inside single quotes, an expression's evaluation should take less time and use fewer system resources. Naturally, the PHP engine could be tweaked to equalize evaluation between single- and double-quote expressions. But this could also change as the PHP engine is changed. To put it more simply, we can say that, depending on the version of PHP, single-quoted versus double-quoted expressions will be evaluated in equal amounts of time and using equivalent system resources. And if you prefer to double-quote everything, by all means do so. But the fact remains that the documentation for PHP says that the contents of a string delimited by single quotes will not be evaluated, whereas those within double quotes will be. What these tips are about is coding things using best practices, derived from logical examination of the way PHP is advertised to function, not transitory benchmarks. Paul -- Paul M. Foster -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
