Eval and Array - it wont show the value

[s0me0ne]

I can get the following to work:

eval("return \$subnav_array;")

However if I do

echo '<strong>' . eval("return \$subnav_array[0][0];") . '</strong>';

all I get is:

<strong></strong>

This isnt working and I dont know why 😕[/SIZE]

[suntra]

Well works for me...

$test[0][0] = 456;
echo eval('return $test[0][0];');

[s0me0ne]

Here is my test server info:

WinXP Pro
PHP 4.4.4
Apache 2.0.59

[s0me0ne]

Perhaps this other line of code before all this, makes it not want to work

$subnav_array = "$".$nav_array[$row][2];

Although I can echo out the value of that fine

so heres a bigger snippet, so you know where stuff is

if ($nav_array[$row][2] != '')
	{
		$subnav_array = "$".$nav_array[$row][2];//get the name of the subnav array
		$num_in_subnav = eval("return count($subnav_array);");

	echo '<strong>'.$num_in_subnav.'</strong><br />';//DEBUG
	echo 'subnav array name= <strong>' .eval("return \$subnav_array;") . '</strong>';//DEBUG
	echo '<strong>' . eval("return \$subnav_array[0][0];") . '</strong>';//DEBUG

	echo '<ul>';

	for ($subrow = 0; $subrow < $num_in_subnav; $subrow++)
	{
		echo '<li><a href="' . eval("return \$subnav_array[$subrow][0];") . '">' . eval("return \$subnav_array[$subrow][1];") . '</a></li>';
	}

	echo '</ul>';
}

I cant see why this isnt working :bemused:

[Weedpacket]

First of all, if you're using eval(), there's a good chance that you're going about what you're doing the wrong way.

In this case, variable variables would make for somewhat easier (and faster) code. Take this part, for example:

$subnav_array = "$".$nav_array[$row][2];//get the name of the subnav array
$num_in_subnav = eval("return count($subnav_array);"); 

That could just as easily be written as

$subnav_array = $nav_array[$row][2];
$num_in_subnav = count($$subnav_array);

And variable variables can often be replaced by arrays (so that what is currently a pile of individual variables are replaced by elements of a single array, probably indexed by what are currently the variable names).

Writing your code directly instead of putting it into a string and having it evaluated at runtime by eval() avoids the extra hassles that come from PHP needing to parse a string to identify things like where a complicated variable expression starts and ends, and your needing to indicate which $ signs need escaping and which don't, and using {} to specify which parts of the string after the $ are part of the variable and which are not, and the other issues that the manual mentions about interpolating variables in strings.

[s0me0ne]

because my arrays look like this

$nav_array = array(
array('home.php', 'Home', ''),
array('design.php', 'Design', 'subnav_design'),
...

$subnav_design = array(
array('web_design.php', 'Web Design'),
array('graphic_design.php', 'Graphic Design'),
array('product_design.php', 'Product Design'),
...

And so I put in the name of the subnav array in the nav array, I didnt know any other way to do a good nav, I dont have database access

[Weedpacket]

One method might be:

$nav_array = array(
	'Home'=>array('home.php', null),
	'Design'=>array('design.php', array(
		'Web Design' => array('web_design.php', null),
		'Graphic Design' => array('product_design.php', null),
		'Product Design' => array('product_design.php', null),
	)),
	...
);

Then $nav_array['Home'] will be an array with two elements. $nav_array['Home'][0] is the name of the page 'home.php', and $nav_array['Home'][1] is null, because there aren't any submenus.

$nav_array['Design'] is also an array with two elements. $nav_array['Design'][0] contains 'design.php', while $nav_array['Design'][1] is an array containing the Design submenu, in exactly the same format as $nav_array itself.

So if you want the submenu for the Design section you have

$submenu = $nav_array['Design'][1];

Once you've done that you have, for example $submenu['Web Design'][0] == 'web_design.php'.

Then again, if you want the submenu for the Home section it's

$submenu = $nav_array['Home'][1];

$submenu will be null, which tells you that there isn't a submenu after all.

Needless to say, since the submenu arrays have exactly the same format as the main nav array, they can each have subsubmenus, should that prove useful.

This is effectively what the usual database representation is designed to simulate (except that relational databases aren't that good with hierarchically-structured data).

If you don't know what the sections in a particular menu are named, you can get a list of them by using array_keys($menu).

So, for example, this just returns a (suitably-nested) list of sections and subsections from such a menu, with links.

function nav_as_list($navmenu)
{
	$list = "<ul>";
	foreach($navmenu as $name=>$content)
	{
		list($link, $submenu) = $content;
		$list .= "<li><a href=\"$link\">$name</a>";
		if(!is_null($submenu))
			$list .= nav_as_list($submenu);
		$list .= "</li>";
	}
	$list .= "</ul>";
	return $list;
}

I say "just", but with appropriate CSS rules (and assuming the code works, seeing as I haven't tested it yet), the output of that function could become a fully-functional whizzbang dropdown menu system.

The same basic structure (have the function loop through the elements, and call itself if it finds a submenu) could be used for pretty much any other traversal task. And it's still possible to write something like "$nav_array['Foo'][1]['Bar'][1]" if you want to get straight at Foo's-->Bar's subsubmenu if, say, you're already in the Bar subsection and just want its subsubmenu.

[s0me0ne]

Thanks that did work and I even added a selected class for whatever page you are on, but I cant figure out how to make the ROOT nav selected.

For instance if you are on Graphic Design I want to make Design have the class of "section_selected" so I can style that appropriately that way the Section and the Page are marked so you know where you are.

$current_page = basename($_SERVER['PHP_SELF']);//added this

function nav_as_list($navmenu)
{
	global $current_page;
	$list = '<ul>';

foreach($navmenu as $name=>$content)
{
	list($link, $submenu) = $content;

            //added this
	if ($current_page == $link)
		$link_status = ' class="selected"';
	else
		$link_status = '';

	$list .= "<li$link_status><a href=\"$link\">$name</a>";//make link selected

	if(!is_null($submenu))
		$list .= nav_as_list($submenu);

	$list .= '</li>';
}

$list .= '</ul>';

return $list;
}

[Weedpacket]

Have another parameter to nav_as_list() called, say, $parent, which has the name of the parent section.

function nav_as_list($navmenu, $parent=null)
{
    global $current_page;
    $list = '<ul>';

foreach($navmenu as $name=>$content)
{
    list($link, $submenu) = $content;

            //added this
    if ($current_page == $link)
        $link_status = ' class="selected"';
    else if(!is_null($parent) && $name==$parent)
		$link_status = ' class="parent"';
	else
        $link_status = '';


    $list .= "<li$link_status><a href=\"$link\">$name</a>";//make link selected

    if(!is_null($submenu))
        $list .= nav_as_list($submenu, $name);

    $list .= '</li>';
}

$list .= '</ul>';

return $list;
} 

$parent could be an entire array ($ancestry?)

function nav_as_list($navmenu, $ancestry=null)
{
    global $current_page;
    $list = '<ul>';

foreach($navmenu as $name=>$content)
{
    list($link, $submenu) = $content;

            //added this
    if ($current_page == $link)
        $link_status = ' class="selected"';
    else if(!is_null($ancestry) && in_array($name,$ancestry))
		$link_status = ' class="ancestor"';
	else
        $link_status = '';


    $list .= "<li$link_status><a href=\"$link\">$name</a>";//make link selected

    if(!is_null($submenu))
	{
        $list .= nav_as_list($submenu, array_merge($ancestry, array($name)));
	}

    $list .= '</li>';
}

$list .= '</ul>';

return $list;
} 

Something like that, anyway.