A simple PHP file upload script, that handles exactly one file

uploadfile.php

<?php
	/*First of all I'm going to DEFINE a few constants because it makes more sense
	to use DEFINE for variables that do not change during the execution of the code.*/
	
	//Max. size of uploaded files in MB
	define('F_UPLOAD_MAX_SIZE_MB',	12);
	
	//Directory to save uploaded files in
	define('F_UPLOAD_DIR',			'./uploads');
	
	//comma-separated list of file extensions to accept - Comment this line and uncomment the next line to disable whitelisting
	define('F_UPLOAD_WHITELIST',	'jpg,jpeg,gif,bmp,png');
	//define('F_UPLOAD_WHITELIST',	false);
	
	//Comma-separated list of file extensions to deny - Uncomment this line and comment the next to enable blacklisting
	//define('F_UPLOAD_BLACKLIST',	'exe,bat,php');
	define('F_UPLOAD_BLACKLIST',	false);

	//Don't change these!
	define('F_UPLOAD_EINVALID',		-1); //The input name that was specified doesn't exist
	define('F_UPLOAD_ETOOLARGE',	-2); //File was too large
	define('F_UPLOAD_EWHITELIST',	-3); //file was not on the whitelist
	define('F_UPLOAD_EBLACKLIST',	-4); //file was on the blacklist
	define('F_UPLOAD_EFAILED',		-5); //move_uploaded_file returned false
	/*Additional error codes >0 may be returned, if PHP encountered an error before
	this code is run.  For definitions of these errors:
	http://www.php.net/manual/en/features.file-upload.errors.php
	*/

	/*I'm going to put the upload code into a function of its own so that it's a
	bit easier to re-use elsewhere*/
	function upload_file($input_name){
		$fname=basename($_FILES[$input_name]['name']);
		if(!isset($_FILES[$input_name])){
			throw new Exception("Input name is invalid", F_UPLOAD_EINVALID);
		}elseif(isset($_FILES[$input_name]['error'])&&$_FILES[$input_name]['error']!==UPLOAD_ERR_OK){
			throw new Exception("An error was encountered uploading the file", $_FILES[$input_name]['error']);
		}elseif($_FILES[$input_name]['size']>(F_UPLOAD_MAX_SIZE_MB*pow(1024, 3))){
			throw new Exception("File is too large", F_UPLOAD_ETOOLARGE);
		}elseif(F_UPLOAD_WHITELIST&&!in_array(strtolower(array_pop(explode('.', $fname))), preg_split('#[,\s]#', F_UPLOAD_WHITELIST))){
			throw new Exception("Filetype is not in the whitelist", F_UPLOAD_EWHITELIST);
		}elseif(F_UPLOAD_BLACKLIST&&in_array(strtolower(array_pop(explode('.', $fname))), preg_split('#[,\s]#', F_UPLOAD_BLACKLIST))){
			throw new Exception("Filetype is in the blacklist", F_UPLOAD_EBLACKLIST);
		}
		//File is OK - tell PHP to move it to the appropriate destination
		$fdest=F_UPLOAD_DIR.'/'.$fname;
		if(!move_uploaded_file($_FILES[$input_name]['tmp_name'], $fdest)){
			throw new Exception("Could not move uploaded file", F_UPLOAD_EFAILED);
		}
		//File is moved
		return $fdest;
	}

	/*Here's the part that can really be modified to do whatever you want - the error
	handling here is incredibly basic.*/
	try{
		$file=upload_file('uploaded');
		printf("Moved uploaded file to %s.", $file);
	}catch(Exception $e){
		echo "Error: ";
		switch($e->getCode()){
			case F_UPLOAD_EINVALID:
			case F_UPLOAD_ETOOLARGE:
			case F_UPLOAD_EWHITELIST:
			case F_UPLOAD_EBLACKLIST:
			case F_UPLOAD_EFAILED:
				//Since I provided a basic error message in the exception, we'll just use that
				echo $e->getMessage();
				break;
			case UPLOAD_ERR_INI_SIZE:
				echo "The uploaded file exceeds the upload_max_filesize directive in php.ini.";
				break;
			case UPLOAD_ERR_FORM_SIZE:
				echo "The uploaded file exceeds the MAX_FILE_SIZE directive that was specified in the HTML form.";
				break;
			case UPLOAD_ERR_PARTIAL:
				echo "The uploaded file was only partially uploaded.";
				break;
			case UPLOAD_ERR_NO_FILE:
				echo "No file was uploaded.";
				break;
			case UPLOAD_ERR_NO_TMP_DIR:
				echo "Missing a temporary folder.";
				break;
			case UPLOAD_ERR_CANT_WRITE:
				echo "Failed to write file to disk.";
				break;
			case UPLOAD_ERR_EXTENSION:
				echo "A PHP extension stopped the file upload.";
				break;
			default:
				printf("Unknown error code: %d", $e->getCode());
				break;
		}
	}