PHP through 7.1.11 enables potential SSRF in applications that accept an fsockopen or pfsockopen hostname argument with an expectation that the port number is constrained. Because a :port syntax is recognized, fsockopen will use the port number that is specified in the hostname argument, instead of the port number in the second argument of the function.
https://security.netapp.com/advisory/ntap-20180112-0001/
https://github.com/php/php-src/commit/bab0b99f376dac9170ac81382a5ed526938d595a
https://bugs.php.net/bug.php?id=75505
https://bugs.php.net/bug.php?id=74216