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10. Running Online Services Using PHP Sockets

Appendix: Exchanging Variables Between JavaScript and PHP

In this book, the JavaScript language is used for the client side of the HTTP client-server model, and PHP is used for the server side. In some cases, the two languages need to exchange variables, and there are a number of ways to do that. The examples in this appendix display the main ways to exchange variable values between JavaScript and PHP.

Example 1: Passing Variables from PHP to JavaScript Using the echo Command

To allow PHP to set JavaScript variables, you can simply inject PHP echo commands into the script in the PHP file. These commands are then evaluated on the server side and create the JavaScript code that is executed locally at the browser. The JavaScript code that appears within the PHP code has to be included in an echo message; otherwise, it is omitted when the PHP code is evaluated. In the following code, which shows the test1.php PHP file, the PHP variable $p holds the current IP address of the client, and it is assigned to the JavaScript variable j . The value of variable j is then printed on the web page.

<?php

$p = $_SERVER['REMOTE_ADDR'];

echo '

var j = "';

echo $p;

echo '";

document.write(j);

</script>';

The previous PHP code evaluates, for the IP address 94.69.186.8, to the following code:

var j = "94.69.186.8";

document.write(j);

</script>

Example 2: Passing Variables from JavaScript to PHP Using the location Object

PHP works on the server side, in other words, at the web server. Therefore, for JavaScript to assign values to PHP variables, the values must be submitted to the web server. The following HTML file, called index.html , includes the JavaScript source code. The window.location object (or simply location ) is used to get information about the URL of the current web page (document); it also redirects the browser to another web page. In this example, the location.href property sets the URL that the current page redirects to. The new page is test2.php , and the p1 and p2 values are included in the query string.

<!DOCTYPE html>

<html>

<body>

var j1 = "hello";

var j2 = "world";

location.href = "test2.php?p1=" + j1 + "&p2=" + j2;

</script>

</body>

</html>

The source code of test2.php is as follows:

<?php

if (isset($_GET["p1"]) && isset($_GET["p2"])) {

$p3 = $_GET["p1"] . " " . $_GET["p2"];

echo $p3;

}

The request issued by JavaScript passes the values of p1 and p2 , which can be retrieved by PHP as $_GET["p1"] and $_GET["p2"] , respectively. The echo message printed to the web page when PHP resolves is hello world .

Example 3: Passing Variables from JavaScript to PHP with HTML Form Submission

In the previous example, the HTTP method GET is only for submitting JavaScript data to PHP. With HTML forms, you can utilize either GET or POST . Consider the following example of index.php , where JavaScript fills the value of a hidden element and submits it with the form.

<!DOCTYPE html>

<html>

<body>

</form>

var j1= "hello world";

document.getElementById('p1').value = j1;

document.getElementById("f1").submit();

</script>

</body>

</html>

The form is submitted from the JavaScript source code with the submit() method of the form object.

document.getElementById("f1").submit();

The source code of test3.php , the program that receives the form data, is as follows:

<?php

if (isset($_POST["p1"])) {

$p2 = $_POST["p1"];

echo $p2;

}

The value of the JavaScript variable j1 is submitted using the form and is assigned then from the PHP source code to the PHP variable $p2 . The value of $p2 is printed to the user’s web page with the echo command.

Example 4: Passing Variables from JavaScript to PHP and Back with Ajax

Another way to pass variables from JavaScript to PHP is to use the Ajax mechanism. Ajax is not a programming language; rather, it is a technique that involves the JavaScript XMLHttpRequest object, which creates an asynchronous connection to the web server in the background. Asynchronous means that the script sends a request to the web server and continues its execution without waiting for a reply. For the asynchronous request, a callback function is set that handles the returned data from the server when it arrives. Initially Ajax was implemented with the XML language, which handled all the requests to the server.

Another way to use the Ajax method is with the DOM model. JavaScript uses the DOM to provide positions to the web page for where to place the server’s reply, such as at a paragraph with a specific ID. These positions are the only parts of the web page that are updated, instead of reloading the whole page. DOM objects provide the positions of the data that will be submitted to the web server.

CSS also plays an important part in the Ajax method because the returned data can be formatted with CSS to retain the styling of the web page that submits the Ajax request.

XMLHttpRequest() is the constructor method that is used to create XMLHttpRequest instances (that is, objects) for the XMLHttpRequest class. The objects are used to connect to a web server, dispatching an HTTP request and receiving the reply. The XMLHttpRequest class defines methods (routines) and properties (variables) for the request handling. The following are the XMLHttpRequest class methods:

XMLHttpRequest() is the constructor of the XMLHttpRequest object.
abort() cancels the current request.
getAllResponseHeaders() returns the headers of the response message.
getResponseHeader() returns a specific response header.
open() initializes the request by setting its attributes.
send() sends the request to the web server.
setRequestHeader() sets the headers of the request.

The following are the XMLHttpRequest class properties:

onreadystatechange defines the function that will be called when the readyState property changes.
readyState takes an integer value that corresponds to the status of the XMLHttpRequest , specifically:
0: Request not initialized
1: Server connection established
2: Request received
3: Processing request
4: Request finished and response ready

responseText holds the response data as a string.
responseXML holds the response data as XML data.
status holds the status of the request reply as an HTTP status code. Examples of HTTP status codes are the following:

200, 301, 400, 403, 404, and 501

statusText holds the corresponding text of the HTTP status code. Here are some examples:

OK for status code 200

Moved Permanently for status code 301

Bad Request for status code 400

Forbidden 403

Not Found for status code 404

Not Implemented for status code 501

The following file, test4.html , uses the POST method to submit data to the program test4.php with the Ajax mechanism. The JavaScript function sendRequest() runs when the web page is loaded.

window.onload = sendRequest;

In this example, the JavaScript variable j1 is sent via Ajax as value1 to the PHP source code and is received in the global variable $_POST["value1"] . This is echoed to the web page returned to the browser, and the message hello world , the initial value of j1 , is printed to the predefined paragraph element, p1 .

<!DOCTYPE html>

<html>

<head>

function sendRequest() {

var xhr = new XMLHttpRequest();

xhr.onreadystatechange = function() {

if (xhr.readyState == 4 && xhr.status == 200) {

document.getElementById("p1").innerHTML = xhr.responseText;

}

xhr.open("POST", "test4.php", true);

xhr.setRequestHeader("Content-type", "application/x-www-form-urlencoded");

var j1 = "hello world";

xhr.send(`value1=${j1}`);

}

window.onload = sendRequest;

</script>

</head>

<body>

</body>

</html>

The source code for test4.php is as follows:

<?php

if (isset($_POST["value1"])) {

$p2 = $_POST["value1"];

echo $p2;

}

The equivalent version for the HTTP method GET would be as follows:

<!DOCTYPE html>

<html>

<head>

function sendRequest() {

var xhr = new XMLHttpRequest();

xhr.onreadystatechange = function() {

if (xhr.readyState == 4 && xhr.status == 200) {

document.getElementById("p1").innerHTML = xhr.responseText;

}

var j1 = "hello world";

xhr.open("GET", `test4b.php?value1=${j1}`, true);

xhr.send();

}

window.onload = sendRequest;

</script>

</head>

<body>

</body>

</html>

The source code for the action file, test4b.php , is as follows:

<?php

if (isset($_GET["value1"])) {

$p2 = $_GET["value1"];

echo $p2;

}

Example 5: Passing Variables from JavaScript to PHP with Cookies

Another option for exchanging variables between JavaScript and PHP is through cookies . Cookies can be set and retrieved from JavaScript and also from PHP. In addition, a cookie set with JavaScript can be retrieved by PHP and vice versa.

The following source code, used in a PHP file such as test5.php , uses JavaScript to set the value of the cookie message in the head section of the HTML source code. Then in the body section of the HTML source code, the PHP code retrieves the cookie’s value and prints this message: Cookie 'message' has value hello .

<!DOCTYPE html>

<html>

<head>

function setCookie(name, value, expires, path, domain, secure){

cookieString = name + "=" + encodeURIComponent(value) + "; ";

if(expires){

expires = setExpiration(expires);

cookieString += "expires=" + expires + "; ";

}

if(path){

cookieString += "path=" + path + "; ";

}

if(domain){

cookieString += "domain=" + domain + "; ";

}

if(secure){

cookieString += "secure; ";

}

document.cookie = cookieString;

}

function setExpiration(days){

var today = new Date();

var expires = new Date(today.getTime() + days * 24 * 60 * 60 * 1000);

return expires. toUTCString();

}

window.onload = setCookie("message", "hello", 1);

</script>

</head>

<body>

<?php

$c_name = "message";

if(!isset($_COOKIE[$c_name])) {

echo "Cookie named '" . $c_name . "' is not set";

} else {

echo "Cookie '" . $c_name . "' has value " . $_COOKIE[$c_name];

}

</body>

</html>

In the JavaScript source code, the cookie string is formed with the required information from these properties: name , value , expires , path , domain , and secure . The function encodeURIComponent() is used to encode the following special characters with their UTF encoded versions:

, / ? : @ & = + $ #

For the expiration date, the current date is calculated in milliseconds via today.getTime() , and the days the cookie is valid, also in milliseconds, is calculated and added to the current date to form the Unix timestamp. The toUTCString() method converts this date to a string according to Coordinated Universal Time (UTC) standard. Here’s an example:

Mon, 29 Oct 2018 06:35:38 GMT

The cookie is set when the web page is loaded with the following JavaScript command:

window.onload = setCookie("message", "hello", 1);

The PHP code retrieves the cookie in the global variable $_COOKIE[$c_name] , where $c_name is the message in the current example.

Example 6: Passing Variables from PHP to JavaScript with Cookies

The following PHP code creates a cookie named message , assigns the value hello to it, and specifies that the cookie expires in one hour (60 minutes * 60 seconds) from now. The function time() returns an integer containing the current time as a Unix timestamp.

<?php

$c_name = "message";

$c_value = "hello";

setcookie($c_name, $c_value, time()+3600);

In the following example, which is included in a PHP file called test6.php , the PHP code sets the value of the cookie named message to hello , and then JavaScript retrieves this value and prints it on the web page:

<?php

$c_name = "message";

$c_value = "hello";

setcookie($c_name, $c_value, time()+3600);

<!DOCTYPE html>

<html>

<head>

</head>

<body>

function retrieve_cookie(w){

var c_value = "";

var dUC = decodeURIComponent(document.cookie);

cArray = new Array();

cArray = dUC.split(';');

for(i = 0; i < cArray.length; i++){

cValues = new Array();

cValues = cArray[i].split('=');

if(cValues[0] == w){

c_value = decodeURIComponent(cValues[1]);

}

return c_value;

}

var cookie_name = "message";

var val = retrieve_cookie(cookie_name);

if(val) {

document.write('Cookie with name "' + cookie_name + '" has value ' + '"' + val + '"');

} else {

document.write('Cookie with name "' + cookie_name + '" does not exist');

}

</script>

</body>

</html>

The function retrieve_cookie() returns the value for the cookie name passed as a parameter. This function splits document.cookie , a string containing a semicolon-separated list of all cookies of the site, and creates an array where each element includes information for a single site cookie. Consider, for instance, the case where two cookies were set with the following PHP code:

<?php

$c_name = "message";

$c_value = "hello";

setcookie($c_name, $c_value, time()+3600);

$c_name = "message2";

$c_value = "hello2";

setcookie($c_name, $c_value, time()+3600);

The document.cookie string in this case would be as follows:

message=hello; message2=hello2

To print the value of document.cookie , use the following command in retrieve_cookie() :

document.write(document.cookie);

In a for loop in retrieve_cookie() , each name-value pair is split across an equal sign, and a new array is created with the first element as the name and the second element as the value. If the given name that was passed as a parameter to the function matches the first element, the second element (the value) is returned. Notice that encodeURIComponent() is used to ensure that document.cookie does not contain any commas, semicolons, or whitespace.

Index

A, B

a2enmod (apache2 enable module) command

Ajax

alert() method

alter table statement

Amazon Standard Identification Number (ASIN)

Animated PNG image

ezgif.com web page

color transparency

display

effects tool

process

frames

getElementById()

pattern

0.png file

runs

six PNG files

source code

sub() runs

uploaded images

web page

zipped file

Apache configuration

apache_note() function

Apache Vhosts

Apache web server

administrative features

Apache process

apache2 process

CA certificate

command ps output lists

directory index, Ubuntu

download and install

ifconfig command

LAN

Linux firewall

logging

new directories and web pages

PHP engine

static private IP address

testing, IP address

vhosts ( see Virtual hosts (vhosts))

appDataLayer struct

Application programming interface (API)

Asymmetric cryptography

ATCP port check site

home page

index.php, source code

system ports

warning message

online open port check tool

online port test site

home page

port verification

remote browser

port 443 testing

port.php, source code

port 25 testing

auto_increment keyword

awk tool

C

cat command

ceil() function

Certificate authorities (CAs)

Certificate-signing request (CSR)

chmod (change mode) command

Client-server communication

Client-side vs. server-side programs

JavaScript/PHP addition web page

action attribute

addition2.html

addition.php

addition2.php

HTML file

JavaScript calculator

Number() function

onclick event

program.html

program2.html

result

$cnt variable

Command-Line PHP client

Command-Line PHP socket server code

Common Gateway Interface (CGI)

$connection variable

create_entry() arguments

CREATE TABLE SQL command

cron, database update

Bash script

crontab

gedit

HTML files

MySQL server

web pages

crontab command

Cross-site scripting (XSS)

D

Database, search-enabled site

Bash shell script

chmod command

do…done commands

info database

MySQL server

creation

info database

MySQL client

MySQL server

Data layer

ddclient daemon

delete SQL statement

describe SQL statement

DocumentRoot directive

Domain name IP address, ddclient

Apache/Lighttpd

current IP address

ddclient installation

DDNS provider’s site

Linux terminal

new public IP address

Domain name registration

CA SSL certificate

CSR

E

echo command

e-mail account confirmation

equijoin

F

Favorite icon (favicon)

fgets() function

File Transfer Protocol (FTP)

Form validation

error messages

form testing

JavaScript, testing146–147

PHP source code

validate.php file, creation

warnings display

web page creation

Fully qualified domain name (FQDN)

ports.httpsserver.eu

qotd.httpsserver.eu

QOTD server

vhosts creation

fwrite() function

G

GeoIP Apache module

a2enmod command

apache2ctl–M command

apache_note() function

GeoIP.dat.gz

geo2.php

geoip_module

mods-available

test location

webpagetest.org

GeoIPCity

GeoIP.dat.gz

geoip_module

getElementById() function

GET method

GET method, site implementation

amazon.co.uk site

offset value

POST references

query string

test

grep command

H

header() function

Home page, dynamic content web site

directory index

HTML files

PHP

echo command

like operator

MySQL server

search.php

PHP-MySQL interface

Hostnames

htmlspecialchars() function

HTTP alternate port

HTTP cookies

browser tools

display details

e-commerce site

Lighttpd configuration file

Linux

and PHP sessions ( see PHP sessions)

remove, PHP

retrieve, PHP

settings

site creation, PHP

web server programs

Wireshark packet analyzer

I

info.php web page

INSERT INTO command

insert into SQL statement

International Standard Book Number (ISBN)

Internet protocol

intval() function

IP-based virtual hosts

address bar

a2ensite (apache2 enable site) command

configuration rules

DirectoryIndex directive

directory indexes

index1.html

index2.html

Linux terminal

testing

start/end VirtualHost containers

isset() function

J, K

JavaScript to PHP

Ajax

HTTP method

location object

L

Lighttpd

animated PNG image ( see Animated PNG image)

basic configuration

change, document root

configuration

created online services ( see Online services with Lighttpd)

enabling and disabling the directory

error message

GUI

installation

log files access

multiple client requests

object-oriented programming principles

PHP 7.0

phpinfo() function

server.modules directive

specific IP address/hostname

testing

basic configuration

directory index

document root

HTML source code

index.lighttpd.html

virtual hosts

Lighttpd web server, CA certificate

Linux firewall

Local area network (LAN)

FQDN

HTTPS connection testing

port 443

port locating

router web interface, connection

M

match string() method

method attribute

mods-available

mysql-client package

MySQL database

alter table statement

describe SQL statement

download

help command

insert SQL statement

installation

mysql client

MySQL server

select statement

status

table

connection

CREATE TABLE command

describe SQL statement

drop table statement

foreign key

primary key

mysqli() function

mysqli_fetch_assoc() function

mysqli_free_result() function

mysqli_query() function

mysqli PHP command

MySQL-PHP interface

mysql-server package

N

Name-based vhosts

create

000-default.conf

/etc/hosts file

HTML code

index.html

Linux terminal

localhost

reload, web server

ServerName directive

testing

first name-based

second name-based

web page downloaded

Network Address Translation (NAT) protocol

nl2br() function

no-IP

account activation

Confirm Account button

e-mail account confirmation

home page

hostname

Normalizing

O

onclick event

Online services with Lighttpd

action file creation

directory screenshot

exec() PHP function

PHP code

php.png image

save file

screenshot.php

shell_exec()

wkhtmltoimage

Xvfb server

basic web pages

create directory index

home page

index.php

invalid URL

screenshot.php

URL inserts

web server responses

Online web service

site creation

WHIOS testing

open() method

Open port check tool

openssl req command

P

Pagination

forward or backward

HTML form

index.php version

limit clause

limit MySQL

PHP engine

search.php

$count

echo command

$offset

PCRE Regular Expression (PREG)

PHP

CLI results

echo command

engine

epigrammatic uses

form validation ( see Form validation)

installation

interpreters

testing

user-defined variables

variables setting

GET method

POST method

web page source code

PHP Command-Line socket server

PHP data objects (PDO)

PHP-enabled web server

phpinfo() function

PHPSESSID cookie

PHP sessions

cookie modification

CSS section

directory index

index.php

page1.html

page2.html

PHPSESSID cookie

project experimentation

session ID

web page

PHP sockets

command-line server

web server, configuration

PHP to JavaScript

echo command

ping.eu WHOIS service

Port-based virtual hosts

a2ensite command

configuration rules

create

directory indexes

document root directory

HTML source code

Linux command line

listening ports

testing

Port forwarding

Apache vhosts

configuration web page

form details

LevelOne FBR-1161 ADSL router, web page

routers

settings

web-based configuration interface, test router

Port number

POST method

preg_split() function

Privacy Enhanced Mail (PEM)

Private IP address

Public and private addresses

Public IP address

Public key infrastructure (PKI)

Q

Query results, two-colored table

Quote of the day (QOTD) protocol

online service creation

ajax technique

QOTD servers

project, source code

site testing

source code

cygnus-x.net

djxmmx.net

online service homepage

qotd.php

TCP socket

R

Rainbow table

Regular expressions

Requests for comments (RFCs)

Root certificates

route command

Router configuration options

S

Search-enabled site

home page

RFC editor

rfc-editor.org site

search.php

Second-level domain (SLD)

Secure logging, project

database creation

design

home page

PHP to MySQL connection, testing

profile.php web page

user account, web page

user connection, testing

user log out

user profile page

Secure Sockets Layer (SSL)

CA certificate, testing

certificate viewer, chromium

chain of trust

home web page

online tool

secure connection

configuration, Lighttpd

Apache

Lighttpd

select SQL statement

Self-signed certificates

openSSL

home directory

HTTPS protocol

testing

chromium browser warning

directory index

HTTPS protocol

insecure connection

IP address

local host link

security exception

untrusted site

sendRequest() function

Server-side programming with PHP

echo command

GET method

POST method

variables and strings

escaping double/single quotes

evaluated test.php web page

HTML tags

JavaScript source code

mixing PHP and HTML tags

$name variable

.php file extension

test.php file

user preferences

session_start() function

session_user variable

setcookie() function

shell_exec() function

Shell script

show databases statement

show tables statement

socket_bind()

socket_close()

socket_listen()

Speedport Entry 2i VDSL router

Spyware programs

SQL queries

group by clause

inner join clause

like operator

select statement

update command

sqlstring

SSLEngine directive

ssl module

SSL/TLS

certificates

public key cryptography

TCP/IP protocol

Static IP address service

Static Map Maker tool

Static map web page

eyedropper tool of mtPaint

geo6.php

new version

shutter window

Static private IP address

Add button

DHCP

DNS server

Editing Wired connection 1 window

ifconfig

IPv4 and IPv6 settings

LAN

manual method, IPv4 settings

Network Connections window

options

route command returns

Save button

testing

Stream Editor (sed)

String delimiters

strpos() function

strtotime() function

strtoupper() function

Structured Query Language (SQL)

Submit buttons, images

CSS properties

CSS disabled selector

opacity property

search.php

submit property

T

TCP/IP sockets

Telnet protocol

Top-level domains (TLDs)

toUTCString() method

Transport Layer Security (TLS) protocol

Transport protocol

trim() function

U

Unix pipe operator (|)

user data, file edition

URL mask option

V

validate() function

Virtual hosts (vhosts)

W

Web page, editing

Web page testing, IP address

webpagetest.org home page

Web Redirect option

Web scraping

args array

awk

categories menu

echo commands

file.txt

for loop

grep

HTML source code

ISBN

Linux

MySQL database

product link

shell program testing

shell.sh

URL, category

wget

Web scraping, MySQL and Linux Shell

URL

address bar

Apress home page

ASIN

ISBN

Web Server

wget (web get) command

where clause

while loop

Whois installation, command line

Wireshark packet analyzer

X, Y, Z

XMLHttpRequest()

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Table of Contents for Back Matter

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Index

A, B

C

D

E

F

G

H

I

J, K

L

M

N

O

P

Q

R

S

T

U

V

W

X, Y, Z

Table of Contents for
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