문의 주신 증상은, php 버젼의 문제로 보이지는 않습니다. 
관련 검색어로 구글 검색등을 해보셨으면 합니다. 

파일 전송등의 옵션문제로 보여집니다. 
ftps 가 선택되어져 있다면 ftp 로 조정하여 보시거나, 

Try changing your FS_METHOD to direct 
의 검색어로, 조치사항을 체크해 보셨으면 합니다. 

감사합니다.

SJ wrote..
: 사실 저도 잘 모르는 문제라서요 
: 
: Cannot read files on system. Try changing your FS_METHOD to direct
: 위와 같은 에러 메시지가 나옵니다.
: 그리고 일부 플러그인이 업데이트 되지 않습니다.
: 
: 
: 
: WordPress Upgrade Constants
: You should define as few of the below constants needed to correct your update issues.
: 
: The most common causes of needing to define these are:
: 
: Host running with a special installation setup involving symlinks. You may need to define the 
: path-related constants (FTP_BASE, FTP_CONTENT_DIR, and FTP_PLUGIN_DIR). Often defining simply 
: the base will be enough.
: Certain PHP installations shipped with a PHP FTP extension which is incompatible with certain 
: FTP servers. Under these rare situations, you may need to define FS_METHOD to "ftpsockets".
: The following are valid constants for WordPress updates:
: 
: FS_METHOD forces the filesystem method. It should only be "direct", "ssh2", "ftpext", or 
: "ftpsockets". Generally, you should only change this if you are experiencing update problems. If 
: you change it and it doesn't help, change it back/remove it. Under most circumstances, setting 
: it to 'ftpsockets' will work if the automatically chosen method does not. Note that your 
: selection here has serious security implications. If you are not familiar with them, you should 
: seek help before making a change.
: (Primary Preference) "direct" forces it to use Direct File I/O requests from within PHP. It is 
: the option chosen by default.
: (Secondary Preference) "ssh2" is to force the usage of the SSH PHP Extension if installed
: (3rd Preference) "ftpext" is to force the usage of the FTP PHP Extension for FTP Access, and 
: finally
: (4th Preference) "ftpsockets" utilises the PHP Sockets Class for FTP Access.