Re: [PHP] Need routine to tell me number of dimensions in array.

Richard Quadling wrote:
> On 15 March 2010 23:45, Daevid Vincent <[email protected]> wrote:
>> Anyone have a function that will return an integer of the number of
>> dimensions an array has?
> 
> /**
>  * Get the maximum depth of an array
>  *
>  * @param array &$Data A reference to the data array
>  * @return int The maximum number of levels in the array.
>  */
> function arrayGetDepth(array &$Data) {
> 	static $CurrentDepth = 1;
> 	static $MaxDepth = 1;
> 
> 	array_walk($Data, function($Value, $Key) use(&$CurrentDepth, &$MaxDepth) {
> 		if (is_array($Value)) {
> 			$MaxDepth = max($MaxDepth, ++$CurrentDepth);
> 			arrayGetDepth($Value);
> 			--$CurrentDepth;
> 		}
> 	});
> 
> 	return $MaxDepth;
> }
> 
> Extending Jim and Roberts comments to this. No globals. By using a
> reference to the array, large arrays are not copied (memory footprint
> is smaller).

Using a reference actually increases overhead. References in PHP were 
mostly useful in PHP4 when assigning objects would cause the object to 
be copied. But even then, for arrays, a Copy on Write (COW) strategy was 
used (and is still used) such that you don't copy any values. Try it for 
yourself:

<?php

$copies = array();
$string = str_repeat( '*', 1000000 );

echo memory_get_usage()."\n";
for( $i = 0; $i < 1000; $i++ )
{
     $copies[] = $string;
}
echo memory_get_usage()."\n";

?>

Cheers,
Rob.
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