How to I convert normal php function into codeigniter function - php

Question

Here is the normal php function which is used in codeigniter which uploads the picture from an android device. I want someone to help to convert into codeigniter function to make it work.
private function uploadImages(){
//get the data from the $_POST and $_FILES
$postKeyPairs = $_POST;
$files = $_FILES['files'];
$titles = "";$description = "";
//fetch the titles
if(array_key_exists('title',$postKeyPairs)){
$titles = $postKeyPairs['title'];
}
//get the description
if(array_key_exists('description',$postKeyPairs)){
$description = $postKeyPairs['description'];
}
//the root file path for the uploaded images
$file_path = "uploads/";
//count the number of files to upload
for($i = 0; $i < count($files['name']); $i++){
//make sure the filename is unique
$filename = basename($files['name'][$i]);
//get the proper filepath for the individual files
$file_path = $file_path.$filename;
//get the title for the current image
if(isset($titles[$i]) && $titles[$i] != null){
$imageTitle = $titles[$i];
}
else{
$imageTitle = "NA";
}
//and get the image description
if(isset($description[$i]) && $description[$i] != null){
$imageDescp = $description[$i];
}
else{
$imageDescp = "NA";
}
//upload the file into the file system
if(!move_uploaded_file($files['tmp_name'][$i], $file_path)){
//any exception occurs
throw new Exception("Couldn't upload image ".$files['name'][$i]);
}
}
return true;
}