explaining all the explanations

README.md

@@ -1,4 +1,44 @@
 # Single .php Filehost
-Simple .php script, mainly for sharing random files with people via curl. (and thus in an easily scriptable way)
+Simple PHP script, mainly for sharing random files with people using curl. (and thus in an easily scriptable way)
 
-You can pretty much just slap this on any webserver with apache2 and rewrite enabled on it, and it should work. The .htaccess is just what I use, and could possibly need a tweak, depending on your situation. Everything else, including configuration, is explained in the code. (but should be pretty self-explanatory anyway)
+It receives files uploaded via HTTP POST, and saves them to a configured directory, with a randomised filename (but preserving the original file extension).  
+On successful upload, it returns a link to the uploaded file. Serving the file to people you've shared the link with can then simply be left to apache to figure out.
+
+There's also a mechanism for removing files over a certain age, which can be invoked by calling the script with a commandline argument.
+
+## Config
+All configuration is done using the global variables at the top of index.php. Hopefully, they're explained well enough in the short comments besides them.
+
+To accommodate for larger uploads, you'll also need to set the following values in your php.ini:  
+upload_max_filesize  
+post_max_size  
+max_input_time  
+max_execution_time  
+(The output of index.php will also warn you, if any of those are not set too small)
+
+The code responsible for the default info text can be found at the very bottom of index.php, in case you want to reword anything.
+
+
+## Purging Old Files
+To check for any files, that exceed their max age, and delete them, you need to call index.php with the argument "purge"  
+```
+php index.php purge
+```
+
+To automate this, simply create a cron job:
+```
+0 0 * * * cd /path/to/the/root; php index.php purge > /dev/null
+```
+If you specify **$STORE_PATH** using an absolute path, you can omit the **cd**
+
+
+### Max. File Age
+The max age of a file is computed using the following formula:
+```
+$fileMaxAge = $MIN_FILEAGE +  
+              ($MAX_FILEAGE - $MIN_FILEAGE) *  
+              pow(1-($fileSize/$MAX_FILESIZE),$DECAY_EXP);
+```
+...which is a basic exponential decay curve that favours smaller files, meaning small files are kept longer and really big ones are deleted relatively quickly.  
+**$DECAY_EXP** is one of the configurable globals and basically makes the curve more or less exponential-looking. Set to 1 for a completely linear relationship.  
+**NOTE:** $DECAY_EXP should always be an uneven number