Posted by Curtis on 02/23/07 01:48

dennis.sprengers@gmail.com wrote:
> Consider the following array and string:
>
> $trail = array('products/veggies', 'products', 'services/cleaning');
> $path = 'products/veggies/1243/more';
>
> I am trying to write a function that matches $path with a value in
> $trail. If no match is found, it should chop off "more" and compare
> again. Then, chop off "1243" and compare again. Now a match is found:
> "products/veggies". The function should return true.
>
> Let's take another example: $path = 'services/industrial/gardening'.
> There is no match for $path in $trail. Chopping off "gardening" leaves
> "services/industrial". Again, no match. Chopping off "industrial"
> leaves "services". No match will be found; the function should return
> false.
>
> This is what I have so far:
>
> function in_trail($path) {
> global $trail;
>
> while ($path && !in_array($path, $trail)) {
> $path = substr($path, 0, strrpos($path, '/'));
> }
>
> return $path ? true : false;
> }
>
> But this function always returns true! Could someone explain this to
> me and tell me how to fix it? Your help is much appreciated :-)
>

I changed it up a little, the function I wrote passes the string by
reference and uses recursion.

// returns true on success, false on failure
// $path is altered in the calling scope
// remove the reference operator (&) if you'd
// rather that not happen
function in_trail($trail, &$path) {
if ( in_array($path, $trail) ) {
return true;
}
else {
// we can't reduce string anymore
if ( ($idx = strrpos($path, '/')) === false )
return false;

// truncate last dir
$path = substr($path, 0, $idx);

// use recursion to check new dirs
return in_trail($trail, $path);
}
}

I haven't tested this on a wide variety of strings/arrays, but it did
work with your example vars.

Hope it helps.

Curtis, http://dyersweb.com

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