array_key_exists performance is poor for &$array

Bug #37563	array_key_exists performance is poor for &$array
Submitted:	2006-05-23 17:16 UTC	Modified:	2006-05-25 22:39 UTC
From:	bugs dot php dot net at nanonanonano dot net	Assigned:	ilia (profile)
Status:	Closed	Package:	Performance problem
PHP Version:	5CVS-2006-05-23 (snap)	OS:	Linux
Private report:	No	CVE-ID:	None

[2006-05-23 17:16 UTC] bugs dot php dot net at nanonanonano dot net

Description:
------------
If there is a reference taken to an array ($b =& $a) then the performance of array_key_exists($foo, $a) drops off enormously unless array_key_exists($foo, &$a) is used.

(Note this is identical to #30295 which is marked as fixed in CVS but doesn't appear to be fixed at all: it is found in both 4CVS and 5CVS)

Reproduce code:
---------------
Based on the code in bug #30295:

    http://pastebin.com/733286

Expected result:
----------------
Time for the following operations should be approximately the same:

array_key_exists($i, $a);

$b =& $a; array_key_exists($i, $a);

$b =& $a; array_key_exists($i, &$a);

Actual result:
--------------
Time for 

$b =& $a; array_key_exists($i, $a);

is significantly greater than for the others.

Sample times from running the reproduce code:

Test with no refs:                    0.0012528896331787
Test with a ref to the array:         0.78344106674194
Test with a ref to the array and pass by ref: 0.0019340515136719

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[2006-05-24 23:14 UTC] iliaa@php.net

This bug has been fixed in CVS.

Snapshots of the sources are packaged every three hours; this change
will be in the next snapshot. You can grab the snapshot at
http://snaps.php.net/.
 
Thank you for the report, and for helping us make PHP better.

[2006-05-25 10:15 UTC] bugs dot php dot net at nanonanonano dot net

Thanks for the prompt attention.

Just one last thing -- the fix only went into 5CVS and as noted in the original bug report the problem exists in 4CVS too. Any chance of backporting the fix?


# test with 4CVS (php4-STABLE-200605250830)
Test with no refs:                            0.0027539730072021
Test with a ref to the array:                 0.89111185073853
Test with a ref to the array and pass by ref: 0.0028078556060791

Thanks in advance!

[2006-05-25 22:39 UTC] iliaa@php.net

This bug has been fixed in CVS.

Snapshots of the sources are packaged every three hours; this change
will be in the next snapshot. You can grab the snapshot at
http://snaps.php.net/.
 
Thank you for the report, and for helping us make PHP better.

it cannot be back ported to PHP4 as the fix relies on PHP 5 
only code.