JSONJSON, or JavaScript Object Notation, is fairly popular.
This is just my modest take on a ‘PHP Object Notation’ implementation.
Note that it is meant to follow how your mind works rather than being syntactically correct; therefore, associative arrays are used in a loose manner where you have to worry about associative syntax as little as possible.
Basically, type away until your object is fully described.

Here is a notation sample:

?View Code PHP
array(
        'root level' => array(
                'sublevel 1' => array(
                        'sublevel 2' => 'sublevel 3',
                ),
        )
);

.
This syntax can then be used the same way JSON is used, using eval. Here is how and you will immediately notice how the eval() syntax has to differ from the JavaScript one:

?View Code PHP
$remote_str = <<<EOB
    array(
        'root level' => array(
                'sublevel 1' => array(
                        'sublevel 2' => 'sublevel 3',
                ),
        )
);
EOB;
// ...
eval('$local_str='.$remote_str.';');

.
Feels a bit clumsy. Fortunately, starting with PHP4, if you are not too sad about introducing a statement in your remote string, you can rewrite it like this:

?View Code PHP
$remote_str = <<<EOB
return array(
        'root level' => array(
                'sublevel 1' => array(
                        'sublevel 2' => 'sublevel 3',
                ),
        )
);
EOB;
// ...
$local_str = eval($remote_str);

.
Better, isn’t it?

In this last listing, you will find the very simple code I wrote to traverse the object. Note that I invoke a callback for every element, otherwise this code would not be very helpful.

Note that this is just a concept for something I needed to throw together quickly therefore there are some limitations; for instance, you cannot have numeric keys since in this context their “keyness” is ignored and even feared.

?View Code PHP
<?php
function traverse_tree($callback, $curlevel, $curdepth, $uid)
{
        $depthstr = '------------------------------------------------------------------------------';
        $padding = substr($depthstr, 0, $curdepth);
        if(!is_array($curlevel))
        {
                $callback($curlevel, $padding, $uid);
                return;
        }
        foreach($curlevel as $level=>$children)
        {
                if(!is_numeric($level))
                {
                        $my_uid = $callback($level, $padding, $uid);
                        traverse_tree($callback, $children, $curdepth + 2, $my_uid);
                }
                else
                {
                        $callback($children, $padding, $uid);
                }
        }
}
 
function do_something($name, $padding, $uid)
{
        $iid = 0; // Bogus value
        print $padding.$name." ($iid)n";
        return $iid;
}
 
// -----------------------------------------------------------
// Here we go
// -----------------------------------------------------------
if(count($argv) != 2)
        die("nSyntax: ".$PHP_SELF." 'root_node_name'nn");
$rootnodename = &$argv[1];
 
$INS = array(
        $rootnodename => array(
                'Bikes' => array(
                        'Yamaha' => 'Fz',
                        'Honda',
                        'Norton'
                        ),
                'Trikes',
                'Cars' => array(
                        'Chevrolet' => array(
                                'Corvette' => array('Z06', 'Convertible', 'Coupe'),
                                'Camaro',
                                'Jimmy'
                                ),
                        'Ford' => array(
                                'Mustang' => array('GT', 'Premium', 'Shelby', 'Other'=>'Roush'),
                                'Explorer',
                                'Crown Victoria'
                                ),
                        'Chrysler' => array(
                                'Dodge' => 'Charger',
                                '300X',
                                'Le Baron'
                                ),
                        )
        )
);
 
traverse_tree(do_something, $INS, 0, 1);
 
print "DONEnn";
?>

.
Invoke with:

?View Code SH
php my_php_script.php "Vehicles"

.
“What is this $iid variable?” you may ask.
You will notice that this piece of code is particularly convenient if you want to add a whole tree structure to your database. Say the you are using MySQL and want to create categories and sub-categories, using the column ‘pid’ as a category’s parent id. You would rewrite do_something:

?View Code PHP
function do_something($name, $padding, $uid)
{
        mysql_query("INSERT INTO my_cat_table(pid, title) VALUES({$uid}, '{$name}')");
        $iid = mysql_insert_id();
        print $padding.$name." ($iid)n";
        return $iid;
}

Voila!

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