PHP FTP code fails, even though file is downloaded successfully - php

Question

I'm using the following code to download a file via FTP in PHP:
$fp = fopen($local_file, 'w+');
$conn_id = ftp_connect($host);
$login_result = ftp_login($conn_id, $user, $pass);
$ret = ftp_nb_fget($conn_id, $fp, $remote_file, FTP_BINARY);
while ($ret == FTP_MOREDATA) {
$ret = ftp_nb_continue($conn_id);
}
if ($ret != FTP_FINISHED) {
echo "<span style='color:red;'><b>There was an error downloading the file!</b></span><br>";
logThis("log.txt", date('h:i:sa'), "ERROR DOWNLOADING FILE!");
exit();
}
fclose($fp);
<<php code continues below this....>>
This code seems to be working fine. The file is downloaded, and the MD5 hash of the file matches the hash of the file on the other server before it was downloaded. So the download does complete.
In any event, using that code above, even with the file successfully downloading, it's hitting the code inside of the if ($ret != FTP_FINISHED) condition.
If the file downloads fine, why is FTP_FINISHED not true?
EDIT
When I check the value of $ret after the WHILE loop, the times the script completes fine $ret=1 and the times the script fails $ret=0
However, there are times when the script fails because $ret=0 when the file is actually downloaded properly, which can be confirmed with a MD5 comparison.
Also, 0 or 1 are not values that should be returned from these commands. The official PHP documentation give three possible return values, they are FTP_FAILED or FTP_FINISHED or FTP_MOREDATA

Answer 1

I have thought of one solution. Since the file does get downloaded correctly, as determined by an MD5 check from the original source (which we do have), I could modify the code this way:
if ($ret != FTP_FINISHED) {
$localMD5 = md5_file($local_file);
if($localMD5 != $remoteMD5){
echo "<span style='color:red;'><b>There was an error downloading the file!</b></span><br>";
logThis("log.txt", date('h:i:sa'), "ERROR DOWNLOADING FILE!");
exit();
}
}
In most cases the script completes as expected, so this block of code never gets run. However, in cases where the error above occurs and this code is run, it could verify the MD5 hash of the file, and only run the error code if it doesn't match the MD5 of the original source file. If the MD5's match then the download was successful anyways, so the error code shouldn't run

Answer 2

Edited:
My first solution wasn't correct. After checking your comments below, I must say your code is correct, and that the problem probably is on "upload_max_size" and "post_max_size" values.
See here "Upload large files to FTP with PHP" and mainly here: "Changing upload_max_filesize on PHP"
So, the proposed solution is to add this to the .htaccess file:
php_value upload_max_filesize 2G
php_value post_max_size 2G
or, if the server is yours (dedicated), set them in php.ini (you'll need to restart the server so the changes take effect).
You may also find useful the post_max_size info in php.net. I've found interesting particularly this:
If the size of post data is greater than post_max_size, the $_POST and
$_FILES superglobals are empty. This can be tracked in various ways,
e.g. by passing the $_GET variable to the script processing the data,
i.e. , and then checking if
$_GET['processed'] is set.