previous file, next file links?

vectornut

I'm a total newbie to PHP, and am trying to find out how to look at the name of the current html file in order to look up the previous and next files from a list.

Example:

current file is /authors/loismcmasterbujold.html

list:

...
/authors/robertasprin.html
/authors/marionzimmerbradley.html
/authors/davidbrin.html
/authors/terrybrooks.html
/authors/stevenbrust.html
/authors/loismcmasterbujold.html
/authors/cjcherryh.html
/authors/PrestonChild.html
/authors/rickcook.html
/authors/CliveCussler.html
...

I want to look in the list to find that the previous file is /authors/stevenbrust.html and the next file is /authors/cjcherryh.html. A simple directory lookup won't work because a)not all files will be in the same folder, and b) I want the list in something other than by-file alphabetical order. I'm currently hard-coding the links in each file, which gets troublesome when I add a new file in the middle of the alphabet, because I have to change 3 different files

Can anybody point me to a script that will do this?

PurpleMonkey

<?php 	#$dirname = "/usr/local/apache/bin";
	$dirname = "C:\\Apache\\bin";


$dir = opendir($dirname);


while( false != ( $file = readdir($dir) ) )
{
  if( ($file != ".") and ( $file != "..") )
  {
    $file_list .= "<li>$file";
  }
}

closedir($dir);
?>

<html><head><title>Listing directory</title><head>
<body>
<p>Files in <?php echo($dirname); ?> </p>
<ul>
<?php echo($file_list); ?>
</ul>
</body></html>

laserlight

PurpleMonkey, read "A simple directory lookup won't work".

Well, vectornut, you effectively have a linked list structure.
Adding a node in the middle of a linked list involves changing the node before, and after the position where the node is to be added.

You could take a dynamic approach by using a database to hold the paths and filenames.
For example, you could use a textfile to hold:

/authors/robertasprin.html
/authors/marionzimmerbradley.html
/authors/davidbrin.html
/authors/terrybrooks.html
/authors/stevenbrust.html
/authors/loismcmasterbujold.html
/authors/cjcherryh.html
/authors/PrestonChild.html
/authors/rickcook.html
/authors/CliveCussler.html

Then use [man]file/man on this textfile.
You can find the current file's place in the array returned by file(), and then work out the previous and next entries, if any.
The nodes would be entered by simply editing the textfile.

Conversely, you could use a relational database to store these filenames and their order, according to some number.

In both cases, the hyperlinks would be dynamically generated.

vectornut

Originally posted by laserlight
Well, vectornut, you effectively have a linked list structure.
Adding a node in the middle of a linked list involves changing the node before, and after the position where the node is to be added.

You could take a dynamic approach by using a database to hold the paths and filenames.
For example, you could use a textfile. Then use [man]file/man on this textfile.
You can find the current file's place in the array returned by file(), and then work out the previous and next entries, if any.
The nodes would be entered by simply editing the textfile.

laserlight, thanks, that's exactly what I was thinking I wanted to do.

vectornut

So here's what I came up with. First of all, I wanted to include this code in my existing .html files without changing the file extensions. So, I figured out I could use an include and even pass in the text file name, like this:

<!--#set var="Link_File" value="directory_structure/link_file.txt" -->
<!--#include virtual="/Next_Previous_Link_Generator.php" -->

Now, here's the meat of the code:

<?php
// Dynamically generate Next and Previous links based on the current page.
$lines = file($Link_File); // Get a file into an array.
$howmany = sizeof($lines);

//find current page in array
for ($i = 0; $i < $howmany; $i++) {
	if (strstr($lines[$i], $_SERVER["REQUEST_URI"])) {
		$doPrevious = ($i - 1);
		$doNext = ($i + 1);
		$i = $howmany;
	} //end if
} //end for
$Previous_Link = rtrim($lines[$doPrevious]);
$Next_Link = rtrim($lines[$doNext]);
echo "<table><tr><td>";
// Make sure current page isn't first in array.
if ($doPrevious > -1) {
	echo "<a href=\"$Previous_Link\" alt=\"Previous ($Previous_Link)\">Previous ($Previous_Link)</a></td>";
} else { // If it is, don't make a previous link.
	echo "</td>";
} //end if then else
// Make sure current page isn't last in array.
if ($doNext < $howmany) {
	echo "<td><a href=\"$Next_Link\" alt=\"Next ($Next_Link)\">Next ($Next_Link)</a>";
} else { // if it is, don't make a next link.
	echo "<td>";
} // end if then else
echo "</td></tr></table>";
?>

If there are any coding errors, they're due to me changing the code slightly from what I actually used on my pages (I used images instead of text links).

vectornut

Originally posted by vectornut

[/B]

Can anybody tell me...I tried to use the same set var method to send the actual structure of a link to the script. I wanted to send something that would be interpreted like this:

<a href="link_info" alt="alt info">link info</a>

And it wouldn't work. It DID work if I sent it like this:

<a href=link_info alt=alt_info>link info</a>

Now, I tried using the \ in front of the " marks, but it didn't make any difference. As long as I had the " marks, I couldn't get it to work. Removing the " marks allowed it to work, but I'm not sure all browsers would even understand the code without the " marks. Any ideas?

vectornut

Okay, I think I need to resurrect this topic from the dead. The script I made above worked for YEARS and now it's stopped working. And I'm not sure why. I've verified that the correct file name is getting generated from the $SERVER["REQUEST_URI"] call, but I'm not getting anything back at all in the $doPrevious and $doNext and no matter what my file name is, it is acting like it is the first record in the list.

<?php
// Dynamically generate Next and Previous links based on the current page.
$lines = file($Link_File); // Get a file into an array.
$howmany = sizeof($lines);

//find current page in array
for ($i = 0; $i < $howmany; $i++) {
	if (strstr($lines[$i], $_SERVER["REQUEST_URI"])) {
		$doPrevious = ($i - 1);
		$doNext = ($i + 1);
		$i = $howmany;
	} //end if
} //end for
$Previous_Link = rtrim($lines[$doPrevious]);
$Next_Link = rtrim($lines[$doNext]);
// Make sure current page isn't first in array.
if ($doPrevious > -1) {
	echo "<a target=\"Home\" href=\"$Previous_Link\" alt=\"Previous ($Previous_Link)\"><img src=\"/images/vehicles/buttonsandstuff/backbutton.jpg\" alt=\"Previous ($Previous_Link)\" BORDER=0 height=37 width=89></a></td>";
} else { // If it is, don't make a previous link.
	echo "</td>";
} //end if then else
// Make sure current page isn't last in array.
if ($doNext < $howmany) {
	echo "<td><a target=\"Home\" href=\"$Next_Link\" alt=\"Next ($Next_Link)\"><img src=\"/images/vehicles/buttonsandstuff/nextbutton.jpg\" alt=\"Next ($Next_Link)\" BORDER=0 height=37 width=89></a>";
} else { // if it is, don't make a next link.
	echo "<td>";
} // end if then else
?>

bradgrafelman

Hard to say without knowing the values of some of these variables.. for example, can you do a var_dump() on $lines and show us the output?

Also, I don't think there's a need for that for() loop at all.. just use [man]array_search/man to find the key of the current page.

vectornut

Okay, the var dump leads me to believe that for some reason the link file isn't getting properly sent to the link generator. When I added var_dump($lines) to the link generator, it resulted in bool(false). Below is the code I used in the page that calls the link generator:

<!--#set var="Link_File" value="/authors/AuthorLinks.txt" -->
<!--#include virtual="/Next_Previous_Link_Generator.php" -->

bradgrafelman

I've never worked with SSI's and whatnot, but I'm fairly sure that just because you do a "#set var" doesn't mean that PHP is automatically going to create a variable for you.

Try looking in the $_ENV superglobal array to see if "Link_File" is set there.

EDIT: Also note that if it is, you'll probably have to do some path manipulation, since "/" refers to the root of your website to Apache, but "/" refers to the root of your hard drive when working with the filesystem in PHP.