The page I am working on has a javascript function executed to print parts of the page. For some reason, printing in Safari, causes the window to somehow update. I say somehow, because it does not really refresh as in reload the page, but rather it starts the "rendering" of the page from start, i.e. scroll to top, flash animations start from 0, and so forth. The effect is reproduced by this fiddle: http://jsfiddle.net/fYmnB/ Clicking the print button and finishing or cancelling a print in Safari causes the screen to "go white" for a sec, which in my real website manifests itself as something "like" a reload. While running print button with, let's say, Firefox, just opens and closes the print dialogue without affecting the fiddle page in any way. Is there something with my way of calling the browsers print method that causes this, or how can it be explained - and preferably, avoided? P.S.: On my real site the same occurs with Chrome. In the ex
Well, we can look at the source:
ReplyDelete/ext/standard/array.c
PHP_FUNCTION(count) calls php_count_recursive(), which in turn calls zend_hash_num_elements() for non-recursive array, which is implemented this way:
ZEND_API int zend_hash_num_elements(const HashTable *ht)
{
IS_CONSISTENT(ht);
return ht->nNumOfElements;
}
So you can see, it's O(1) for $mode = COUNT_NORMAL.
In PHP 5+ the length is stored in the array so the counting is not done each time.
ReplyDeleteEDIT: You also might find this analysis interesting: PHP Count Performance. Although the length of the array is maintained by the array, it still seems as though it is faster to hold on to it if you are going to call count() many times.
PHP stores the size of an array internally, but you're still making a function call when which is slower than not making one, so you'll want to store the result in a variable if you're doing something like using it in a loop:
ReplyDeleteFor example,
$cnt = count($array);
for ($i =0; $i < $cnt; $i++) {
foo($array[$i]);
}
Additionally, you can't always be sure count is being called on an array. If it's called on an object that implements Countable for example, the count method of that object will be called.