If you've already got a filepath of the form "ssh2.sftp://$sftp/path/to/file" you can just use unlink() on that path
(PECL ssh2 >= 0.9.0)
ssh2_sftp_unlink — Delete a file
$sftp
, string $filename
)Deletes a file on the remote filesystem.
Returns TRUE on success or FALSE on failure.
Example #1 Deleting a file
<?php
$connection = ssh2_connect('shell.example.com', 22);
ssh2_auth_password($connection, 'username', 'password');
$sftp = ssh2_sftp($connection);
ssh2_sftp_unlink($sftp, '/home/username/stale_file');
?>
If you've already got a filepath of the form "ssh2.sftp://$sftp/path/to/file" you can just use unlink() on that path