php getting file name with extension using its first characters - php

Question

Huh, this is my first serious web project and for that moment i've got simply big enigma.
The deal is to get previous and next file extension using its first letters, for instance:
there's file 04.jpeg 05.gif 06.tiff we're currently reading 05.gif so we remove extension
and now its '05' so we add one so we get '06' and HOW TO GET THAT FILE EXTENSION?!?!?!
Details:
The problem is that i need to fix my image browser which works in two modes:
Comics browser
[comics in folder looks like:
page00.extension
page01.extension
(...)
page09.extension
page10.extension
page11.extension
]
Single files browser
[single files in folder looks like:
01.extension
02.extension
03.extension
(...)
09.extension
10.extension
11.extension
]
[extension maybe jpg,jpeg,gif,png etc.]
Im getting current $extension and file name using $_GET var.
Here is some code - im working with bootstrap 3 framework:
Also im sorry that there's no comments but this isn't really complicated as it looks like
<?php
if($type == 2) {
$number = substr($clean, 4);
$nextnum = $number + 1;
$prevnum = $number - 1;
$prevpath = HOW TO GET IT WITH EXTENSION??
$nextpath = HOW TO GET IT WITH EXTENSION??
$nextext = '.' . substr(strrchr($prevpath,'.'),1);
$prevext = '.' . substr(strrchr($nextpath,'.'),1);
if ($nextnum >= 10) {
$next = 'page' . $nextnum . $nextext;
} else {
$next = 'page0' . $nextnum . $nextext; }
if ($prevnum >= 10) {
$prev = 'page' . $prevnum . $prevext;
} else {
$prev = 'page0' . $prevnum . $prevext; }
if ($clean === "page00") {
$prev = 'page00' . $extension; }
$count = 'page' . $x;
if ($clean === $count) {
$next = $count . $extension; }
} elseif($type == 3) {
$nextnum = $clean + 1;
$prevnum = $clean - 1;
$prevpath = HOW TO GET IT WITH EXTENSION?? <====== MY PROBLEM
$nextpath = HOW TO GET IT WITH EXTENSION?? <====== MY PROBLEM
$nextext = '.' . substr(strrchr($prevpath,'.'),1);
$prevext = '.' . substr(strrchr($nextpath,'.'),1);
if ($nextnum >= 10) {
$next = $nextnum . $nextext;
$prev = $prevnum . $prevext;
} else {
$next = '0' . $nextnum . $nextext;
$prev = '0' . $prevnum . $prevext; }
if ($clean === "01") {
$prev = '01' . $extension; }
if ($clean === $x) {
$next = $x . $extension; } }
echo '<br />
<div class="btn-group btn-group-justified">
<a class="btn btn-default" href="?browse=' . $prev . '" role="button">Poprzedni</a>
<a class="btn btn-default" href="' . $goback . '" role="button">Wyjdź</a>
<a class="btn btn-default" href="?browse=' . $next . '" role="button">Następny</a>
</div>';
?>

Answer 1

function get_next_file($file){
$maxdigits = 2; // assuming the file always ends with two digits
$dir = dirname($file) . DIRECTORY_SEPARATOR;
$fname = pathinfo($file, PATHINFO_FILENAME);
$name = substr($fname, 0, -$maxdigits);
$digits = substr($fname, -$maxdigits) + 1;
foreach(array('bmp', 'png', 'jpg', 'gif') as $ext){
$test = $dir . $name . str_pad($digits, $maxdigits, '0', STR_PAD_LEFT) . '.' . $ext;
if(file_exists($ext))return $ext;
}
return false; // no such file...
}
The complete function would look like the one above (not tested!). You would call it like so:
Assuming we have these files:
test01.png
test02.gif
test05.bmp
You get these results:
get_next_file('test01.png') => 'test02.gif'
get_next_file('test02.gif') => false // 'coz the other file is not consecutive
get_next_file('test05.bmp') => false // no other files to look for...

Answer 2

If you know the name of current file then you can search for files in a directory using glob:
if (is_array(glob('05.*'))) { /* do some stuff */ }
Else you can create a whilte-list of extensions and use file_exists:
foreach (array('jpg', 'jpeg', 'png') as $ext)
if (file_exists('05.'. $ext)) { /* do some stuff */ }