note 109285 added to function.array-merge-recursive

The presence of NULLs has been discussed in some earlier posts, but here is an example of the issue and a fix. Although it may not be apparent, if using array_merge_recursive in a loop to combine results from a database query or some other function, you can corrupt your result when NULLs are present in the data. I discovered this when migrating from an Oracle DB to a MySQL DB. I had to match the array structure returned from the PHP function calling the DB and got bit. The array_walk call fixed this for me. This is a simple example that lacks any DB calls and looping. Assume your array had the DB column names (first, last, and age) and you needed to combine the data in a multi-dimensional array in which the column name is an array key with all rows beneath it. The corruption occurs in $a3. If using element position 2, one could create the fictitious 'pete johnson' because of the collapsing of elements. print "<pre>Show corruption\n"; $a1 = array('first'=>'bob', 'last'=>'jones', 'age'=>'48'); $a2 = array('first'=>'sam', 'last'=>'smith', 'age'=>'41'); $a3 = array('first'=>'pete', 'last'=>null, 'age'=>'3'); $a4 = array('first'=>'joe', 'last'=>'johnson', 'age'=>'33'); $a5 = array_merge_recursive($a1,$a2,$a3,$a4); print_r($a5); print "Show Fix\n"; $a1 = array('first'=>'bob', 'last'=>'jones', 'age'=>'48'); $a2 = array('first'=>'sam', 'last'=>'smith', 'age'=>'41'); $a3 = array('first'=>'pete', 'last'=>null, 'age'=>'3'); array_walk($a3, 'null_to_empty'); $a4 = array('first'=>'joe', 'last'=>'johnson', 'age'=>'33'); $a5 = array_merge_recursive($a1,$a2,$a3,$a4); print_r($a5); print "</pre>\n"; function null_to_empty(&$item) { $item = is_null($item) ? '' : $item; } ---- Server IP: 91.199.167.223 Probable Submitter: 135.245.10.5 ---- Manual Page -- http://www.php.net/manual/en/function.array-merge-recursive.php Edit -- https://master.php.net/note/edit/109285 Del: integrated -- https://master.php.net/note/delete/109285/integrated Del: useless -- https://master.php.net/note/delete/109285/useless Del: bad code -- https://master.php.net/note/delete/109285/bad+code Del: spam -- https://master.php.net/note/delete/109285/spam Del: non-english -- https://master.php.net/note/delete/109285/non-english Del: in docs -- https://master.php.net/note/delete/109285/in+docs Del: other reasons-- https://master.php.net/note/delete/109285 Reject -- https://master.php.net/note/reject/109285 Search -- https://master.php.net/manage/user-notes.php