ftp_alloc() function in PHP

The ftp_alloc() function allocates space for a file to be uploaded to the FTP server. This function is useful when uploading large files to ensure sufficient disk space is available on the server before attempting the transfer.

Syntax

ftp_alloc(connection, size_of_file, res);

Parameters

• connection − The FTP connection resource to use

• size_of_file − The number of bytes to allocate on the server

• res − Optional variable to store the server response message

Return Value

The ftp_alloc() function returns TRUE on success or FALSE on failure.

Example

The following example demonstrates how to allocate space before uploading a file −

<?php
    $myFile = "demo.txt";
    $con = ftp_connect('192.168.0.4');
    $login_result = ftp_login($con, 'username', 'password');
    
    if (ftp_alloc($con, filesize($myFile), $res)) {
        echo "Sending $myFile<br>";
        ftp_put($con, 'remote_file.txt', $myFile, FTP_BINARY);
    } else {
        echo "Failed in allocating space! Message = $res<br>";
    }
    
    ftp_close($con);
?>

Key Points

• Not all FTP servers support the ALLO command that this function uses

• The function is primarily useful for large file transfers

• Always check the return value before proceeding with file upload

• The $res parameter captures server response messages for debugging

Conclusion

The ftp_alloc() function helps ensure sufficient server space before file uploads. While not supported by all FTP servers, it's a good practice for large file transfers to prevent upload failures due to insufficient disk space.