(PHP 5 >= 5.4.0, PHP 7) Call a header function

(PHP 4, PHP 5, PHP 7) Checks if or where headers have been sent

(PHP 4, PHP 5, PHP 7) Alias of

(PHP 4, PHP 5, PHP 7) Open connection to system logger

(PHP 4, PHP 5, PHP 7) Close connection to system logger

(PHP 4, PHP 5, PHP 7) Get Internet service which corresponds to port and protocol

(PHP 4, PHP 5, PHP 7) Check DNS records corresponding to a given Internet host name or IP address

(PHP 5, PHP 7) Alias of

(PHP 4, PHP 5, PHP 7) Get the IPv4 address corresponding to a given Internet host name

(PHP 4, PHP 5, PHP 7) Converts a string containing an (IPv4) Internet Protocol dotted address into a long integer