File exists after deletion

public function save(){

    //var_dump($_FILES['file_upload']);
    if($this->id){
        $this->update();
    } else{
            if(!empty($this->errors)){
            return false;
            }

            if(empty($this->filename)|| empty($this->tmp_path)){
            $this->errors[]="The file was not available";
            return false;
            }

            $target_path=SITE_ROOT.DS.'admin'.DS.$this->upload_directory.DS.$this->filename;

            //echo $target_path;

    /* The problem is here but I can't find it - If I comment this out
       I can upload the same file multiple times*/
        if(file_exists($target_path)){
        $this->errors[]="The file {$this->filename} already exists";
        return false;
        }

            if(move_uploaded_file($this->tmp_path,$target_path)){
                    if($this->create()){
                        unset($this->tmp_path);
                        return true;
                    }
            } else{
                $this->errors[]="Check File Permissions!!";
                return false;
            } // end inner else

    } // end else
} // end save