Recursive arrays

maZtah · 11-18-2009, 01:25 PM

Hi guys.

I have a MySQL table 'categories'. Every category has a 'parent_id' field. All the main elements have parent_id=0.

What I want is to make an multidimensional array which I can loop through to put in an unordened list (<ul>).

Something like:

PHP Code:

<ul>
<?php
foreach($aCategories as $aRow)
{ ?>
    <li>
        <a href="#"><?php echo $aRow['name']; ?></a>
<?php
    $aChild = $aRow['child'];
    if (is_array($aChild))
    { ?>
        <ul>
<?php
        foreach($aChild as $aChildRow)
        { ?>
            <li><a href="#"><?php echo $aChildRow['name'];</a>
<?php
        } ?>
        </ul>
<?php
    } ?>
    </li>
<?php
} ?>
</ul>

I hope you understand what I'm trying to achieve.

Thanks for your help.

tony · 11-18-2009, 03:18 PM

the code looks like it does the job. But if you don't know how many levels of children there are I'll suggest to use a recursive function.

php Code:

<?php
function print_categories($aCat) {
    echo "<ul>\n";
    echo "\t<li>";
    if(is_array($row)) {
        print_categories($row);
    } else {
        echo '<a href="#">'.$aRow['name'].'</a>';
    }
    echo "\t</li>";
    echo "</ul>\n";
}

print_categories($aCategories);
?>

Although I haven't tested the this code, the idea is to make it recursive when the input is an array.

maZtah · 11-19-2009, 08:13 AM

Thanks tony. But; how would I make the multidimensional array from the mysql results?

I did something like this, but this works only for 2 levels.

PHP Code:

public function sort_menu($aResult)
{
    foreach($aResult as $aRow)
    {         
        $aIds[] = $aRow['id'];
        
        if (!in_array($aRow['parent_id'], $aIds))
        {
            $aCategories[$aRow['id']] = $aRow;
        }
        else
        {
            $aCategories[$aRow['parent_id']]['child'][] = $aRow;
        }
    }
    
    return $aCategories;
}