How to Use the ftp_size() Function in PHP to Get File Size

1. What is the ftp_size() Function?

In PHP, the `ftp_size()` function is used to retrieve the size of a specified file on an FTP server. The function connects to the FTP server and returns the size of the specified file (in bytes).

The basic syntax of the function is as follows:

ftp_size($ftp_stream, $remote_file);

Here, `$ftp_stream` is the FTP connection resource established using the `ftp_connect()` function, and `$remote_file` is the name of the file for which the size is being retrieved.

2. Return Value of ftp_size() Function

When the function is executed successfully, `ftp_size()` returns the size of the specified file, measured in bytes. If the file does not exist or cannot be accessed, the function returns false.

Here is an example of the return value of the `ftp_size()` function:

$ftp_conn = ftp_connect('ftp.example.com');
$ftp_login = ftp_login($ftp_conn, 'username', 'password');
$file_size = ftp_size($ftp_conn, 'example_file.txt');
<p>if ($file_size === false) {<br>
echo 'Failed to get file size!';<br>
} else {<br>
echo 'File size: ' . $file_size . ' bytes';<br>
}

In the example above, the code first connects to the FTP server using the `ftp_connect()` function and logs in with the `ftp_login()` function. Next, it calls `ftp_size()` to retrieve the size of the specified file and stores the result in the `$file_size` variable. Finally, it checks whether the result is false. If so, it indicates that the file size retrieval failed; otherwise, the file size is displayed.

3. Important Considerations When Using ftp_size()

3.1. FTP Extension Must Be Installed

Before using the `ftp_size()` function, ensure that the FTP extension is installed in PHP. If the FTP extension is not installed, the `ftp_size()` function will not work properly.

3.2. File Name Is Case Sensitive

When calling the `ftp_size()` function, ensure that the case of the file name matches exactly with the file name on the FTP server. Otherwise, the function may fail to retrieve the file size correctly.

3.3. FTP Data Transfer Mode

The `ftp_size()` function uses binary (BINARY) transfer mode by default. If you are dealing with text files, it is recommended to set the transfer mode to ASCII before the transfer.

You can use the `ftp_pasv()` function to set the FTP connection to passive mode. If the FTP server does not support passive mode, you will need to use active mode instead.

4. Example: Get File Size from an FTP Server

Here is a complete example demonstrating how to retrieve the size of a file from an FTP server:

$ftp_conn = ftp_connect('ftp.example.com');
$ftp_login = ftp_login($ftp_conn, 'username', 'password');
ftp_pasv($ftp_conn, true); // Enable passive mode
<p>$get_size = ftp_size($ftp_conn, 'example_file.txt');</p>
<p>if ($get_size !== false) {<br>
echo "File size: " . $get_size . " bytes";<br>
} else {<br>
echo "Unable to retrieve file size!";<br>
}</p>
<p>ftp_close($ftp_conn);

In this example, the code first connects to the FTP server using `ftp_connect()`, logs in with `ftp_login()`, and then enables passive mode with `ftp_pasv()`. After that, it uses the `ftp_size()` function to retrieve the file size and outputs the result.

5. Conclusion

The `ftp_size()` function is a useful tool in PHP for retrieving the size of a specified file on an FTP server. It should be used in combination with other FTP-related functions, such as `ftp_connect()` and `ftp_login()`, to ensure successful file size retrieval.

By using the `ftp_size()` function, you can effectively retrieve file sizes from an FTP server and ensure the correct transfer mode is used to avoid errors. Whether working with large files or frequently interacting with an FTP server, understanding how to use this function is crucial.