[pmwiki-devel] php multi-dimensional array construction problem

[Hans]

Friday, February 6, 2009, 2:16:15 AM, Patrick wrote:

> What happens with...?

>     a:b:c = val1
>     a:b   = val2

> It would seem that array[a][b] can't simultaneously be a value and an array.

True. I would probably want to check if a value (or array) exists
before setting a new value, so it just gets added at the right level.


I like to thank everyone for their ideas! None worked for me, but I
got inspired by each response, and took something from it!
I think I got a solution I can share here now:

The functions make it possible to pass the keys either as array or as
string with ':' separators between the words.

For getting a node value the function cuts the array tree iteratively
smaller till the leaf node is left:

function TreeNodeGet($keys, $tree) {
        if (!$keys) return null;
        if (!is_array($keys))
                $keys = explode(":", $keys);    
        while ($key = array_shift($keys)) {
                if (!array_key_exists($key, $tree)) return null;
                $tree = $tree[$key]; //reduce branch iteratively
        }
        return implode("",$tree); //node leaf 
} //}}}


But I could not figure a way to use iterations for setting a new
value, I kept messing up the original array. So here I am using eval,
which should not pose problems with input restricted to safe
characters. This function will just overwrite an existing value:

function TreeNodeSet($keys, &$tree, $val) {
        if (is_array($keys))
                $keys = implode(":", $keys);
        return eval( '$tree[\''.str_replace(':', '\'][\'', $keys).'\'] = $val; return true;');
} //}}}


Then to add some checks for preventing overwriting two more
functions, also using eval to pass the keys:

function TreeNodeExists($keys, $tree) {
        if (is_array($keys)) $keys = implode(":", $keys);
        return eval( 'if(isset($tree[\''.str_replace(':', '\'][\'', $keys).'\'])) return true; else return false;');
} //}}}

function TreeNodeIsArray($keys, $tree) {
        if (is_array($keys)) $keys = implode(":", $keys);
        return eval( 'if(is_array($tree[\''.str_replace(':', '\'][\'', $keys).'\'])) return true; else return false;');
} //}}}


There are probably better php solutions out there.
But stuff I found about iteration classes I could not understand.
Most info seems to be about accessing or writing hierarchical data
structures to a SQL db.

Hans