Re: Reference or copy?

The general rules of thumb are --> don't use references unless you actually *want* a reference. And don't use references for performance reasons. Under PHP 4, it's generally been recommended to use a reference operator when creating objects.

         $obj =& new Object();

PHP uses references internally until it's necessary to create a copy: $a = array(); $a = $b; // internally, $b is a reference to $a

$b[] = "chocolate";    // at this point, a copy is made, and $b is modified

So PHP waits until a copy is actually needed before it makes one. Explicitly making copies incurs overhead because of the concept of "reference counting". So again, don't use references for performance reasons. ~Ted On 23-Jul-08, at 1:07 AM, Yeti wrote:

Hello everyone, Many of you may be familiar with references in PHP. Now i read somewhere in the PHP manual that creating references can take longer than copies. PHP5+ also seems to reference a bit different thant PHP4 did. Here is some working example code: <?php class useless { var $huge_array; function __construct() { $this->huge_array = array(); for ($i = 0; $i < 1024; $i++) $this->huge_array[] = $GLOBALS; // fill ze array with copies of $GLOBALS array return true; } function useless() { return $this->__construct(); } } $time_start = microtime(true); $test_obj = new useless(); $time_end = microtime(true); $time = $time_end - $time_start; echo "It took {$time} seconds without using the reference operator.\r\n"; unset($test_obj); $time_start = microtime(true); $test_obj =& new useless(); $time_end = microtime(true); $time = $time_end - $time_start; echo "It took {$time} seconds using the reference operator.\r\n########## with obj2 ############\r\n"; $time_start = microtime(true); $test_obj = new useless(); $obj2 = $test_obj; $time_end = microtime(true); $time = $time_end - $time_start; echo "It took {$time} seconds without using the reference operator.\r\n"; unset($test_obj); $time_start = microtime(true); $test_obj =& new useless(); $obj2 =& $test_obj; $time_end = microtime(true); $time = $time_end - $time_start; echo "It took {$time} seconds using the reference operator.\r\n"; ?> I tested the code in PHP 4.4.7 and in PHP 5.2.5 and the results were pretty much the same. Using references speeds up the script! Occasionally obj2-with-references took longer than all the others. But i don't know if that's to be taken serious. Now if i do not need a copy, isn't it smarter to use references instead? I'm grateful for any ideas, thoughts or experiences Yeti --PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php