Question

Do I have to check whether the $_SERVER variable has a key REQUEST_METHOD before actually using $_SERVER['REQUEST_METHOD']?

That is, is it overly defensive to always check whether a key exists in array variable like $_SERVER?

Answer 1

The PHP-manual says the following about the $_SERVER-variable:

There is no guarantee that every web server will provide any of these;
servers may omit some, or provide others not listed here. That said, a
large number of these variables are accounted for in the » CGI/1.1
specification, so you should be able to expect those.

The CGI/1.1 specification has the following to say:

The REQUEST_METHOD meta-variable MUST be set to the method which
should be used by the script to process the request, as described in
section 4.3.

and

The Request Method, as supplied in the REQUEST_METHOD meta-variable,
identifies the processing method to be applied by the script in
producing a response. The script author can choose to implement the
methods most appropriate for the particular application. If the
script receives a request with a method it does not support it SHOULD
reject it with an error (see section 6.3.3).

It probably isn’t necessary to check for its existense if you aren’t doing any CLI-development and the script will only be run from a server like Apache. You could probably do it, to be on the safe side, but it is of no necessity.