It allocates space for a file to be uploaded
Example
<?php
$fName = “/home/user/test.txt”;
$ftpId = ftp_connect(‘ftp.phpcodez.com’);
$login_result = ftp_login($ftpId, ‘anonymous’, ‘user@phpcodez.com’);
ftp_alloc($ftpId, filesize($fName), $result) or die($result);
ftp_put($ftpId, ‘temfileName’, $file, FTP_BINARY);
ftp_close($ftpId);
?>