From: cjbj at hotmail dot com
Operating system: Windows 2000
PHP version: 4.3.2
PHP Bug Type: Arrays related
Bug description: Array_reduce uses first element as default running total
Description:
------------
If the optional 'initial' parameter to array_reduce() is omitted, its
default value is the first element of the array, and iteration
proceeds over the second and subsequent array elements.
This means that the first element may not have the "function" applied
to it.
Reproduce code:
---------------
For example:
<?php
// See "Programming PHP (O'Reilly, March 2002)" on p128
function add_up($running_total, $current_value) {
echo "running_total is $running_total, current_value is
$current_value\n";
$running_total += $current_value * $current_value;
return $running_total;
}
$numbers = array (2,3,5,7);
$total = array_reduce($numbers, 'add_up');
print "Total is $total\n";
?>
Expected result:
----------------
The expected output is:
running_total is 0, current_value is 2
running_total is 4, current_value is 3
running_total is 13, current_value is 5
running_total is 38, current_value is 7
Total is 87
This calls add_up() once per array element.
Actual result:
--------------
The actual result is:
running_total is 2, current_value is 3
running_total is 11, current_value is 5
running_total is 36, current_value is 7
Total is 85
Adding the optional third parameter to array_reduce():
$total = array_reduce($numbers, 'add_up', 0);
gives the expected (and desired for the default case) output:
running_total is 0, current_value is 2
running_total is 4, current_value is 3
running_total is 13, current_value is 5
running_total is 38, current_value is 7
Total is 87
This total is the sum of the squares.
The uncomfirmed errata to Programming PHP
(http://www.oreilly.com/catalog/progphp/errata/progphp.unconfirmed)
indicates to me the default value of 'initial' may be a bug.
If it is not a bug, then the current behavior doesn't seem to match
common expectations and the manual entry "applies iteratively the
function function to the elements of the array input" could be
clarified.
Tested on 4.3.2 on Windows 2000 with the prebuilt binary of 29 June
2003 from php.net.
--
Edit bug report at http://bugs.php.net/?id=24980&edit=1
--
Try a CVS snapshot (php4): http://bugs.php.net/fix.php?id=24980&r=trysnapshot4
Try a CVS snapshot (php5): http://bugs.php.net/fix.php?id=24980&r=trysnapshot5
Fixed in CVS: http://bugs.php.net/fix.php?id=24980&r=fixedcvs
Fixed in release: http://bugs.php.net/fix.php?id=24980&r=alreadyfixed
Need backtrace: http://bugs.php.net/fix.php?id=24980&r=needtrace
Try newer version: http://bugs.php.net/fix.php?id=24980&r=oldversion
Not developer issue: http://bugs.php.net/fix.php?id=24980&r=support
Expected behavior: http://bugs.php.net/fix.php?id=24980&r=notwrong
Not enough info: http://bugs.php.net/fix.php?id=24980&r=notenoughinfo
Submitted twice: http://bugs.php.net/fix.php?id=24980&r=submittedtwice
register_globals: http://bugs.php.net/fix.php?id=24980&r=globals
PHP 3 support discontinued: http://bugs.php.net/fix.php?id=24980&r=php3
Daylight Savings: http://bugs.php.net/fix.php?id=24980&r=dst
IIS Stability: http://bugs.php.net/fix.php?id=24980&r=isapi
Install GNU Sed: http://bugs.php.net/fix.php?id=24980&r=gnused
