This code can be used as a P4A mask to provide very basic File Manager functionality outside of the RTE.

class fm extends p4a_base_mask
{
public $rootfolder = null;
public $htmlrootfolder = null;

//yes I know P4A has it's own system for this built around defined constants. Constants that we can't change! so lets do it here on a mask by mask basis.
public $valid_preview_images = array('gif','jpg','ico','png'); //'mp3','mp4','avi','pdf','doc','xls','odt','ods','txt'
public $valid_preview_text = array('txt');

public function __construct() {
parent::__construct();

$site = '/'.P4A::singleton()->user_data['user'];

$this->rootfolder = P4A_UPLOADS_DIR.$site;
$this->htmlrootfolder = P4A_UPLOADS_PATH.$site;

$iconpath = P4A_ROOT_URL.'/icons/default/16';
$this->setTitle('File Manager');

//File Handling
$this->build("P4A_Dir_Source", "fileset")
->setDir($this->rootfolder);

$this->build("P4A_Field", "upload_field")
->setLabel('Upload:')
->setUploadSubpath('')
->label->setWidth(50);
$this->upload_field->setType("file");
$this->intercept($this->upload_field, "afterUpload", "afterUpload");

$this->build("p4a_table",'table')
->setSource($this->fileset);
$this->table->addActionCol ('delete')
->cols->delete->setLabel('<img src="'.P4A_ROOT_URL.'/icons/default/16/actions/edit-delete.png" alt="[D]" title="Delete this file" />');
$this->intercept($this->table->cols->delete, 'afterClick', 'DeleteColClick');
$this->table->addActionCol ('preview')
->cols->preview->setLabel('<img src="'.P4A_ROOT_URL.'/icons/default/16/actions/thumbnail.png" alt="[P]" title="View this file" />');
$this->intercept($this->table->cols->preview, 'afterClick', 'TableRowClick');
$this->table->rows->addAction('afterClick');
$this->intercept($this->table->rows, 'afterClick', 'TableRowClick');

$this->build("P4A_Fieldset","f_table")
->setLabel('Files ['.str_replace($this->rootfolder,'.',$this->fileset->getDir()).']')
->anchorLeft($this->table)
->anchorCenter($this->upload_field);

//Directory Handling
$this->build("P4A_Toolbar","dtb")->setSize(16);
$this->dtb->addButton('new_',$iconpath.'/mimetypes/folder_green.png');
$this->dtb->addButton('home',$iconpath.'/actions/go-home.png');
$this->dtb->addButton('delete',$iconpath.'/actions/edit-delete.png');
$this->intercept($this->dtb->buttons->new_, 'onClick', 'createFolder');
$this->intercept($this->dtb->buttons->home, 'onClick', 'goFolderHome');
$this->intercept($this->dtb->buttons->delete, 'onClick', 'deleteFolder');

$navme = $this->build("P4A_Dir_Navigator","navme")
->setBaseDir($this->rootfolder);
$this->navme->addAction('afterClick');
$this->intercept($this->navme, 'afterClick', 'NavRowClick');

$this->build("P4A_Field", "create_folder_field")
->setWidth(100)
->label->setWidth(30)
->setLabel('New: ');

$this->build("P4A_Fieldset","f_navme")
->setLabel('Directory ['.str_replace($this->rootfolder,'.',$this->navme->getBaseDir()).']')
->setWidth(250)
->anchor($this->create_folder_field)
->anchorleft($this->dtb)
->anchor($this->navme);
//Preview Handling
$this->build("p4a_image","imagepreview")
->setStyleProperty('position','relative') //a bit of elbow room
->setStyleProperty('padding','10px'); //a bit of elbow room

$this->build("p4a_box","textpreview")
->setWidth(500)
->setStyleProperty('padding','10px'); //a bit of elbow room

$this->build("P4A_Button", "close_imagepreview_button")
->setSize(16)
->setLabel('Close Preview',false)
->setIcon($iconpath.'/actions/window-close.png')
->implement("onclick", $this, "closeImagePreview");

$this->build("P4A_Button", "close_textpreview_button")
->setSize(16)
->setLabel('Close Preview',false)
->setIcon($iconpath.'/actions/window-close.png')
->implement("onclick", $this, "closeTextPreview");

$this->build("P4A_Fieldset","f_imagepreview")
->setLabel('')
->setVisible(false)
->anchorRight($this->close_imagepreview_button)
->anchorCenter($this->imagepreview);

$this->build("P4A_Fieldset","f_textpreview")
->setLabel('')
->setVisible(false)
->anchorRight($this->close_textpreview_button)
->anchorCenter($this->textpreview);

//Display
$this->frame->anchor($this->f_navme)
->setWidth(700)
->addCssClass('mr_frame')
->addCssClass('ui-corner-all')
->anchorLeft($this->f_table)
->anchorCenter($this->f_imagepreview)
->anchorCenter($this->f_textpreview);

$this->build("P4A_Quit_Toolbar","toolbar");

$this->display("top",$this->toolbar);

$this->info('File Manager Loaded...');

}

public function closeImagePreview() {
$this->f_imagepreview->setVisible(false);
}
public function closeTextPreview() {
$this->f_textpreview->setVisible(false);
}

public function goFolderHome() {
$d = $this->rootfolder;
$this->f_navme->setLabel('Directory [.]');
$this->fileset->setDir($d)
->reload();
$this->navme->setCurrentSubdir($this->rootfolder);
$this->uploadfield->setUploadSubpath('');
$this->f_table->setLabel('Files [.]');
}

public function NavRowClick($a) {
$v = $this->navme->getCurrentSubdir();
$d = $this->rootfolder;
$this->f_table->setLabel('Files [./'.$v.']');
$this->f_navme->setLabel('Directory [./'.$v.']');
$this->fileset->setDir($d.'/'.$v)
->reload();
$this->uploadfield->setUploadSubpath($d.'/'.$v);
}

public function TableRowClick($o, $a) {
$f = $this->table->data->fields->filename->getValue();
$s = $this->table->data->fields->size->getValue();
$e = trim(end(explode(".", $f)));
if (in_array($e,$this->valid_preview_images)) {
$relativepathfilename = $this->navme->getCurrentSubdir().'/'.$f;
$this->imagepreview->setIcon($this->htmlrootfolder.'/'.$relativepathfilename);
$this->f_textpreview->setVisible(false);
$this->f_imagepreview->setLabel('Preview: '.$f)
->setVisible(true);
} elseif(in_array($e,$this->valid_preview_text)) {
$relativepathfilename = $this->navme->getCurrentSubdir().'/'.$f;
$fileContent = file_get_contents($this->rootfolder.'/'.$relativepathfilename,FILE_TEXT);
$this->textpreview->setValue('<pre>'.$fileContent.'</pre>');
$this->f_imagepreview->setVisible(false);
$this->f_textpreview->setLabel('Preview: '.$f)
->setVisible(true);

} else {
$this->info('Sorry. Preview unavailable for this file');
}
}

public function DeleteColClick($o, $a) {
$this->info('Deleting file...');
$fullpathfilename = $this->fileset->getDir().'/'.$this->table->data->fields->filename->getValue();
unlink($fullpathfilename);
$this->fileset->reload();
$this->info('Done...');
}

public function createFolder() {
$this->info('Creating...');
$v = $this->navme->getCurrentAbsoluteDir();
$folder = $this->create_folder_field->getNewValue();
if ($v == $this->rootfolder.'/') {
$fullnewpath = $v.$folder;
} else {
$fullnewpath = $v.'/'.$folder;
}
mkdir($fullnewpath,0777,true);
$this->create_folder_field->setNewValue(null);
$this->info('Done...');
}

public function afterUpload() {
$tmpname = $this->upload_field->getNewValue(0);
$name = $this->upload_field->getNewValue(6);
$fullpath = $this->fileset->getDir();

rename(P4A_UPLOADS_TMP_DIR . "/$tmpname", "$fullpath/".$name);
$this->upload_field->setNewValue(null);
$this->fileset->reload();
}

public function deleteFolder() {
$this->info('Deleting directory...');
$v = $this->navme->getCurrentAbsoluteDir();
$folder = $this->create_folder_field->getNewValue();
if ($v == $this->rootfolder.'/') {
$this->error('You cannot delete your root directory');
} else {
$fulldelpath = $v.'/'.$folder;
$oneup = realpath($fulldelpath.'/../');
$this->_delete_directory($fulldelpath);
$this->navme->setBaseDir($oneup); //move navme up one
$this->fileset->setDir($oneup) //move filelist up one
->reload();
$this->info('Done...');
}
}

function _delete_directory($dirname) { //remove containing files & directories then remove what I've asked for
if (is_dir($dirname))
$dir_handle = opendir($dirname);
if (!$dir_handle)
return false;
while($file = readdir($dir_handle)) {
if ($file != "." && $file != "..") {
if (!is_dir($dirname."/".$file))
unlink($dirname."/".$file);
else
$this->_delete_directory($dirname.'/'.$file);
}
}
closedir($dir_handle);
rmdir($dirname);
return true;
}

}

You may need to add the necessary icons to the correct location in the

./icons

directory. I used the Open Source Crystal iconset.

This was developed using P4A v3.4.1

I'm sure this can be improved upon, feel free to do so and let me know...