copy images from ftp location to local directory using PHP - php

Question

I am trying to get images from ftp location to local directory, I have a mysql table with ID and image name as columns. I can't copy the image from ftp location to local folder.Th script gets connected to the ftp server gets the image and creates sub directories according to ID on local folder but fails to write the image.
Script:
function etCommonGetImagePath($conn, $camName, $id) {
$serverDir = $_SERVER['DOCUMENT_ROOT'];
$imagesTop = "/cam_images";
$idArray = str_split(strval($id));
$idString = implode('/', $idArray);
$webPath = $imagesTop . "/" . $camName . "/" . $idString . ".jpg";
$full_path = $serverDir . $webPath;
if (file_exists($full_path)) {
return $webPath;
}
else {
$tableName = $camName;
// Is there an image in the database?
$sql = "SELECT image, datetime, image_name FROM $tableName WHERE id=$id";
$result = $conn->Execute($sql);
if (!$result) {
print $conn->ErrorMsg();
}
$rows = $result->fields;
$imageData = $rows['image'];
$sightingDt = $rows['datetime'];
$sightingTs = strtotime($sightingDt);
$sightingFile = $rows['image_name'];
if ($imageData != NULL) {
// We have an image - copy it out to the filesystem
chdir($serverDir.$imagesTop);
if (!file_exists($camName)) {
mkdir($camName);
}y
chdir($camName);
foreach ($idArray as $dir) {
if (!file_exists($dir)) {
mkdir($dir);
}
chdir($dir);
}
$imageFh = fopen($full_path, 'w');
$numBytes = fwrite($imageFh, $imageData);--- this is where it fails.
fclose($imageFh);
}
}