So I’m running a CentOS 6 server which among other things hosts a website using wordpress.   I’m using php56u from IUS on C6’s native apache, and pecl + SSH because php-ssh2 is kinda broken. I ran smack dab into this exact problem:
https://core.trac.wordpress.org/ticket/39746

In my case, wordpress 4.7.6 auto updated, and I notied that 4.8.2 was available, so I chose my standard update method of ssh2.sftp via the web interface, and it errored “couldn’t find wordpress directories”.  
error_log showed a php error: PHP Warning:
file_put_contents(ssh2.sftp://Resource id #834/.maintenance): failed to open stream …   this had worked for me for several years of updates prior to this.

if I understand what that guy posted on the wordpress TRAC, there’s an upstream error in php 5.6.29+ (I was on .30 and now .31) and pecl ssh2.    the wordpress folks on that thread think that its a php SSH
problem and don’t want to address it, while the poster thinks they could easily work around it.

now, I realize none of this is directly a CentOS problem as its the IUS
(Rackspace?) version of php I’m running, and pecl is way out of your bounds, but I’m wondering.

anyone here at all plugged into the pecl world and familiar with the SSH
extension want to comment ?    or am I way out of bounds.

the wordpress folks I’ve talked with say just don’t USE the ssh2.sftp update method, use FTP (ugh!) or use ‘direct’ (php directly writes the
.php files to update the app, eek).    they think I should contain php in php-fpm, something thing I’ve not looked at before.

—
john r pierce, recycling bits in santa cruz