Removing spaces in image filename

<?php
require_once '../ImageUploaderPHP/UploadedFiles.php';

//This variable specifies relative path to the folder, where the gallery with uploaded files is located.
//Do not forget about the slash in the end of the folder name.
$galleryPath = '../Gallery/';

$absGalleryPath = realpath($galleryPath) . '/';
$absThumbnailsPath = realpath($galleryPath . 'Thumbnails/') . '/';


function saveUploadedFiles() {
	global $absGalleryPath, $absThumbnailsPath;

	//Create XML file which will keep information about files (image dimensions, description, etc). 
	//XML is used solely for brevity. In real-life application most likely you will use database instead.	
	$descriptions = new DOMDocument('1.0');
	$descriptions->appendChild($descriptions->createElement('files'));
	
	//Iterate through uploaded data and save the original file, thumbnail, and description.
	while(($file = UploadedFiles::fetchNext()) !== null) {
		$fileName = $file->getSourceFile()->getSafeFileName($absGalleryPath);
		$correctFileName = str_replace(" ","_",$fileName);
		$file->getSourceFile()->save($absGalleryPath . '/' . $correctFileName);	
		
		$thumbFileName = $file->getThumbnail(1)->getSafeFileName($absThumbnailsPath);
		$correctThumbName = str_replace(" ","_",$thumbFileName);
		$file->getThumbnail(1)->save($absThumbnailsPath . '/' . $correctThumbName);
		
		//Save file info.
		$xmlFile = $descriptions->createElement('file');
		$xmlFile->setAttribute('name', $correctFileName);
		$xmlFile->setAttribute('thumbName', $correctThumbName);
		$xmlFile->setAttribute('width', $file->getSourceFile()->getWidth());
		$xmlFile->setAttribute('height', $file->getSourceFile()->getHeight());
		$xmlFile->setAttribute('description', $file->getDescription());
		$descriptions->documentElement->appendChild($xmlFile);
	}

	$descriptions->save($absGalleryPath . 'Descriptions.xml');	
}


function initGallery() {
	global $absGalleryPath, $absThumbnailsPath;
	
	//First of all, clear files and data uploaded at previous time.
	
	//Delete source files.
	$handle = opendir($absGalleryPath);

	while (false !== ($file = readdir($handle))) {
		if (is_file($absGalleryPath . $file)) {
			unlink($absGalleryPath . $file);
		}
	}
	closedir($handle); 

	//Delete thumbnails
	$handle = opendir($absThumbnailsPath);	
	while (false !== ($file = readdir($handle)))  {
		if (is_file($absThumbnailsPath . $file)) {
			unlink($absThumbnailsPath . $file);
		}
	}
	closedir($handle);
	
	//NOTE: If you do not want to delete previously uploaded files, just 
	//remove or comment out the code above.	
}


initGallery();
saveUploadedFiles();
?>