Link between PHP and HTTP Request and Response Messages - php

Question

When I did a networks course I learned about HTTP Request and Response messages and I know how to code in php reasonably enough to get around. Now my question is, the PHP has to have some link to HTTP request and response message but how. I can't seem to see the link between the two. My reasoning for asking this is that I am using the Twitter API console tool to query their api. The tool sends the following HTTP request:
GET /1.1/search/tweets.json?q=%40twitterapi HTTP/1.1
Authorization:
OAuth oauth_consumer_key="DC0se*******YdC8r4Smg",oauth_signature_method="HMAC-SHA1",oauth_timestamp="1410970037",oauth_nonce="2453***055",oauth_version="1.0",oauth_token="796782156-ZhpFtSyPN5K3G**********088Z50Bo7aMWxkvgW",oauth_signature="Jes9MMAk**********CxsKm%2BCJs%3D"
Host:
api.twitter.com
X-Target-URI:
https://api.twitter.com
Connection:
Keep-Alive
and then I get a HTTP response:
HTTP/1.1 200 OK
x-frame-options:
SAMEORIGIN
content-type:
application/json;charset=utf-8
x-rate-limit-remaining:
177
last-modified:
Wed, 17 Sep 2014 16:07:17 GMT
status:
200 OK
date:
Wed, 17 Sep 2014 16:07:17 GMT
x-transaction:
491****a8cb3f7bd
pragma:
no-cache
cache-control:
no-cache, no-store, must-revalidate, pre-check=0, post-check=0
x-xss-protection:
1; mode=block
x-content-type-options:
nosniff
x-rate-limit-limit:
180
expires:
Tue, 31 Mar 1981 05:00:00 GMT
set-cookie:
lang=en
set-cookie:
guest_id=v1%3A14109******2451388; Domain=.twitter.com; Path=/; Expires=Fri, 16-Sep-2016 16:07:17 UTC
content-length:
59281
x-rate-limit-reset:
1410970526
server:
tfe_b
strict-transport-security:
max-age=631138519
x-access-level:
read-write-directmessages
So how do these HTTP request and response messages fit into PHP? Does PHP auto generate this? How do I add authorization to PHP requests etc? I'm confused about the deeper workings of PHP

Answer 1

When the client sends the HTTP request to the server, there has to be something to receive the HTTP request, which is called a web server. Examples of web servers are Apache, IIS, Nginx, etc. You can also write your own server, which can handle input however it wants. In this case, I'll assume that you are requesting a PHP file.
When the web server captures the HTTP request, it determines how it should be handled. If the file requested is tweets.json, it will go make sure that file exists, and then pass control over to PHP.
PHP then begins its execution, and performs any logic that the script needs to do, meaning it could go to the database, it reads, writes and makes decisions based cookies, it does math, etc.
When the PHP script is done, it will return a HTML page as well as a bunch of headers back to the web server that called it. From there, the web server turns the HTML page and headers back into a HTTP request to respond.
That is a pretty simple overview, and web servers can work in many different ways, but this is a simple example of how it could work in a introductory use-case. In more complex scenarios, people can write their own web servers, which perform more complex logic inside of the web server software, rather than passing it off to PHP.
When it comes down to it, PHP files are just scripts that the web server executes when they are called, they provide the HTTP request as input, and get a web page and headers as output.