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How to check whether a site visitor is unique?

Practice




How to check whether a site visitor is unique?

1. It's preferable to have user authentication
with confirmation via email or OpenID or via social networks, and the most reliable confirmation method is via SMS.

2. if there is no authentication, then it's impossible to fully identify an anonymous user.

but you can use a special key in cookies
by User-Agent + screen resolution, etc..
by IP
by loading speed

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Lectures and tutorial on "Running server side scripts using PHP as an example (LAMP)"

Terms: Running server side scripts using PHP as an example (LAMP)

file and network sockets.
Object Oriented Programming (OOP) in PHP Interfaces, Classes, Abstract Classes, Objects
Sessions in PHP link with cookies
PHP Interview Questions and Answers
PHP additional questions and answers for interviews
Class Polymorphism in PHP
Class Inheritance in PHP
questions and answers to the interview on JavaScript and PHP in English
Application of closures of anonymous functions and calback in PHP
Problem A. BibTEX and solve by C ++ && PHP
PHP phrase output in a circle in text mode
php text direction from top to bottom Lilichka
PHP class diagram used in OOP
PHP Framework Performance Comparison
Purpose of the CGI interface. CGI applications
Data transfer methods GET and POST, DELETE, PUT. REST architecture CGI applications. REST API.
CGI environment variables
HTTP headers
HTTP response codes
MIME Types
PHP and CGI
PHP syntax
PHP language data types
Binary Data (Boolean) In PHP
Integers in PHP
Float Numbers in Float
String in PHP
Arrays in php
Objects in PHP
Special Resource type in PHP
Special type Null (empty type) in PHP
Mixed pseudotype in PHP
Callback pseudotype in PHP
Manipulations with PHP data types
PHP language variables
Local Variables in PHP
Global variables in php
Static Variables in PHP
External variables (variables outside PHP) Using PHP from the command line
PHP variable operations (operators) Expressions in PHP
Variables (symbolic links)
Predefined and PHP Superglobals
$ _SERVER server variables in PHP
Constants in PHP. Predefined PHP Constants
PHP operators
Operators for executing external commands in PHP
Operators for working with PHP arrays
PHP error management statements
PHP Class Operators
PHP control structures
Conditional statements in PHP
PHP loops
PHP selection constructs
PHP declaration constructs declaration declare directive tick
Value Return Constructions Return Construction
PHP Inclusion Constructions
Alternative syntax for PHP control structures
Links in PHP
Introduction to functions in PHP
Math Functions in PHP
Work with files. in php
Work with database and SQL basics in PHP
Work with date and time PHP
Interaction with different servers using different protocols in PHP CURL
GD - working with images on the server side (PHP)
Beautiful script or programming styles in PHP
Secure PHP programming
Installation in Ubunutu 16 and LAMP (Apache 2.4, PHP 7.0 (mod or FastCGI) and Mysql 5.7.) + SSH + FTP (proftpd) + Mailserver Postfix
Regular expressions. in php
Support and daily use of LAMP Linux (Ubunutu), problem solving due to errors, system monitoring
LAMP suite (complex) of server software
Advantages and disadvantages of PHP FastCGI and mod_php (php as apache or FastCGI module)
php Analysis of slow script execution
Sending mail using PHP in linux or windows
Apache htaccess settings file
PHP Namespace & use & MVC
PHP vs Nodejs
Arguments of functions, typed arguments, an array of arguments in PHP
MPM configuration options for apache mpm-prefork (mpm-worker) with mod_php (php-fpm) + nginx reverse proxy and their comparison
SSL Certificates. Installing a purchased and self-signed SSL certificate for Nginx and Apache. HTTPS setup
Individual PHP settings for sites
configuration of Postfix Ubunutu - mail server
How to install Laravel from Nginx web server to Ubuntu + installation on Windows Laravel
What is HTTP_RAW_POST_DATA?
Writing datasets to shared (shared) memory using PHP
Jpegtran - JPEG image optimization, installation and bulk operations
Real-Time Applications and Polling, Long Polling, WebSockets, Server-Sent Events SSE
PHP Interview Questions
Null-coalescence operator - php Two question marks ??
PHP anonymous classes
PHP right-associative operator ** denoting exponentiation (two multiplications)
PHP spaceship operator less space equals more
PHP Expectations assert () - zero-cost assumptions in industry code
PHP 7 Declaration of scalar types in parameters and return values
PHP 5.6 Three Point Functions with a Variable Number of Arguments Using the Syntax ... Deploying Arguments Using ...
Static variables, static properties and methods, and later static binding in PHP and OOP features
Regular expressions in php and other languages. Regular expressions: search with inversion
How to work with composer and how does composer install vs update differ?
Algorithms for Selecting Server and Location Blocks in Nginx
PHP Data Encryption
Try-catch exception handling: what's the difference between exceptions and errors?
How to Set Up Docker + Docker Compose on Windows 10 Using WSL 2 Ubuntu 20
What's new in PHP 8
Simple Object Access Protocol (SOAP): Differences Between REST and SOAP
How to Enable Logging on the Bind (Named) DNS Server on Debian
Error: DB Error: [Error message: extension mysql is not compiled into PHP]
Error: journal rollforward failed: journal out of sync with zone XYZ
CentOS and httpd - 403 error and SELinux
Your Own DDNS (Dynamic DNS) Server and Client Based on Debian
Apache: setting PHP options and parameters for individual sites
PHP: logging errors to a file
PHP: can't upload a file larger than 8 MB (even with a higher max_upload_filesize)
Installing and configuring a secondary (slave) DNS server on CentOS/RedHat (BIND/named)
Where the PHP configuration file - php.conf (php.ini) - is located on Linux Debian, CentOS/RedHat, and FreeBSD
Viewing Apache server status (state, processes and connections) via mod_status on CentOS / RedHat
Viewing Apache server status (state, processes and connections) via mod_status on Debian
HTMLPurifier strips (removes) anchors from the resulting HTML document
.htaccess - blocking site access from certain User-Agents (web browsers or bots)
nginx: blocking access from certain IPs (ngx_http_access_module)
Where to get phpize (phpize: command not found) - for Debian, CentOS, ubuntu, or RedHat
nginx: Redirect from one domain to another
nginx: error "could not build the server_names_hash, you should increase server_names_hash_bucket_size"
IIS: ASP.NET fails to connect with the error "Failed to generate a user instance of SQL Server due to failure in retrieving the user's local application data path..."
Apache: closing the Range and Request-Range header vulnerability (via RequestHeader)
Apache: where the configuration files are located on Debian, CentOS, FreeBSD, ubuntu, and RedHat
Apache: where to put settings common to all VirtualHosts
BIND (named) DNS server management commands - rndc. Reload, zone transfer, cache flush.
Installing phpMyAdmin on CentOS (RedHat) and Apache
Installing LAMP (Apache + MySQL + PHP 5.3) on CentOS 5.x (RedHat 5)
Installing MySQL + Apache + PHP on FreeBSD (the same LAMP web server, but on FreeBSD)
Apache: "httpd: Could not reliably determine the server's fully qualified domain name, using 127.0.0.1 for ServerName"
Installing and Configuring the BIND (named) DNS Server on CentOS (RedHat)
Error "unknown option 'zone'" in bind (named)
Installing and Configuring the BIND (named) DNS Server on Linux Debian
Installing PHP on IIS 7 on Windows Server
How to change the PHP session lifetime
Merging www. and non-www. into one domain - 301 redirect via mod_rewrite
Latest PHP 5.3 on Debian Squeeze
Installing PHP 5.3 on Debian Lenny (latest versions)
Latest PHP 5.2 on Debian Lenny
Rewrite Engine does not accept URL-encoded strings
Installing LAMP on Debian
webalizer - how to change the language
Enabling SSL in Apache (Debian or Ubuntu)
Enabling SSL in Apache (FreeBSD)
Apache: error "out of memory: kill process"
.htaccess - Usage and Syntax
Cyrillic (Internationalized) domains and IDNA - how to configure them
Regular Expressions in PHP (regex php)
How to check all user messages for dangerous characters before saving?
How to find out how much free and used disk space there is - php html linux
coin-slider - links don't work when hovering over the slide image?
PHP function/script to determine if a point falls inside a polygon
Twig date format modifier
How to get a dump of variables in TWIG
After moving OpenCart to another domain: Notice: unserialize() [function.unserialize]: Error at offset - index.php on line 45, header.php on line 43, index.php on line 61
How to check total and free server RAM in PHP
Order of image slides in the OpenCart banner slideshow
How to add a menu item in OpenCart?
CMS Made Simple reports problems loading the module list in the Module Manager
How to create an array of values in Smarty, and how to decline month names into the genitive case
Flex/Flash HTTPService - passing parameters in an HTTP request
How to make an accompanying label clickable to toggle a checkbox to the opposite state?
A Smarty variable isn't passed from head to body
How to display news from a specific category in WordPress? cat doesn't help
Comparing Hosting Providers in Ukraine
OpenCart admin file manager doesn't show images, possibly due to Russian filenames
How to trim text in PHP while keeping a required number of lines (limiting the number of line breaks)
How to make an automatic news sitemap in CMS Made Simple
OpenCart: unable to place a second order after checkout
Month in Russian in the news section, CMS Made Simple
WordPress won't assign a template to a specific page
How to make a breadcrumb navigation chain in CMS Made Simple™
Fatal error: Class 'Gdn' not found in Vanilla Forums
7 Ways to Protect a Website from Scraping and How to Bypass Them
Why Does the Browser Freeze?
How to display weight and SKU on the product page in OpenCart?
MS IE 8 does not pass the referrer $_SERVER['HTTP_REFERER'] PHP
How to add a new "is new product" attribute in OpenCart
How to disable debug mode in the Symfony framework
Programmatic noun declension by number in PHP
Deleted cache.category files from /system/cache/, now OpenCart doesn't work
Can you suggest where to find a set of small PNG icons?
How to output the current year in Smarty?
How to change the root folder for Symfony using .htaccess
How to get a resource count (getResources) in MODX before its output
Warning: date_default_timezone_get(): It is not safe to rely on the system timezone settings when creating a Doctrine Entity from the command line in Symfony 2
Remove hyperlinks in a WordPress post
console.log(55); shows nothing, doesn't work. Shows undefined instead
In Joomla 1.5 / 2.5, general settings won't save in the admin panel
Lots of division-by-zero errors in the server logs, where could they be?
How to change the default product sorting by price in OpenCart
GET pending and canceled appear when using audio and video HTML tags in Chrome
Opencart product not found on the site but exists in the admin panel
Why isn't there an anti-like button on social networks like Facebook and VKontakte?
session_start(); doesn't work and $_SESSION['emailsend'] isn't saved
How to add a comment field to the checkout in OpenCart
OpenCart after migrating to another host: Fatal error: Call to a member function getId() on a non-object in /catalog/controller/common/header.php on line 43
OpenCart filterpro module doesn't work, pagination doesn't read the page variable
How to make the +/- buttons next to "add to cart" change the order quantity in Opencart, not just "1"
Which php.ini parameters affect the size and time of uploading files to the server?
OpenCart: correct links for child categories when the SEO URL doesn't exist
How to create an onbefore action in Symfony 2?
How to convert coordinates from spherical to Cartesian on a flat map
How to make a placeholder for missing images in OpenCart (noimage)
How to programmatically calculate a product order for a manager?
Simplify_SystemException with message System error occurred processing a request
CMS Made Simple: how to insert an image into a news item?
Variable not being assigned: Unexpected token "name" of value "as" ("end of statement block" expected)
Upload on Android, iPad, iPod: how to upload a file to a site via a mobile device's web browser?
How can you render templates from an action in Symfony? How to render several templates?
The select's first option ONCHANGE doesn't work: Mozilla window.location.href="?r="+this.options[this.selectedIndex].value;
PHP regular expression to detect that there are no Russian letters
Cookie value isn't being saved, its expiration date shows 1970 January 1st, 3:00:12
How to implode a two-dimensional array in PHP?
How to recover the admin password in OpenCart when email isn't working, salted password
How to remove index.php?route= from all links in OpenCart?
DDD reviews, or what do you think about Domain-Driven Design?
How to remove the product return option everywhere in OpenCart
What are the differences between shell_exec, system, exec, backticks, and passthru?
How to install and configure CMS MS (Made Simple)
How to outline (add a shadow to) text with imagestring in PHP
How to redirect folder paths for Apache, e.g. for all images
CMS Made Simple: "<!-- Not a tag module -->" error, module doesn't work
Dumping Smarty variables — what modifiers show a variable's contents?
Who fills in the NS record in DNS?
How to make OpenCart save the customer's HTTP_REFERER source in the order
How to check whether a site visitor is unique?
Is there a break/continue in loops in the Twig template engine?
How to output elapsed time between moments in the correct grammatical case (depending on numerals) using PHP
What is a Redemption Period? When does a domain become available again?
In Opencart, viewing a product and adding it to the cart always adds 1 - how to add more than one item
Twig converts html text entities, and a line break is output as &lt;br&gt;
Error during Merge with local - Mercurial says: abort: outstanding uncommitted changes
Windows 8 ran out of disk space after watching movies online
How to check in Smarty whether the displayed variable holds the current date
Opencart tag search doesn't work correctly (case and encoding issues)
How to enable SEO-friendly URLs for CMS Made Simple
tvFilters modx in array (has one) — how to select one from a list
shell_exec(cd /home/user/scripts/; sudo su ./testsh.sh) doesn't work; NULL
How to disable the redirect to the last previous url after authorization in Symfony
Ubuntu - apache mkdir php 775
How to find out in PHP the number of lines in a block of a given width, i.e. determine the number of line breaks
How to install the Apache server, with screenshots
PHP error: fatal error call-time pass-by-reference has been removed in On line ***
How to make opencart send order notification emails with full data to both the admin and the customer?
Fatal error: Class Gdn not found in ..... vanilla forums
How to make filterpro in OpenCart show all categories
How to center an invisible element or find the width and height of an invisible element?
How to select all Facebook friends' checkboxes with one click when sending invitations
Double slash or empty character doesn't work in RewriteRule
How to change the title tag on the homepage in WordPress and remove separators when the All in One SEO Pack module is installed
CSRF Attack
Fatal error: Call to undefined function bcscale() php7
Installing and Configuring mod_security on Apache in Debian and Ubuntu
WordPress: how to translate a theme or plugin using Loco Translate?
A multifunctional, universal image management system for a website
A universal system for protecting a site from parsing and other malicious activity.
How to install certbot on UBUNTU 16, certificate for Nginx only
Cookie is not being sent back (cookies not working)
NGINX errors [alert] 1 open socket left in connection [alert] aborting
OpenCart SEO URLs in the database for categories and products
The Last-Modified header is not sent from any file on the hosting, including a test one
Working with the Product Collection in Magento
Programming Patterns in the Magento CMS
What is Google Trends and how to work with it
SEO Basic Concepts
What is the react-dom package useful for?
Sort Laravel collection by array of ids
How to transpose a collection in Laravel (Transpose collection Laravel)
Validating comma-separated IDs — a regular expression
Adding the suffix st, nd, rd, or th for English ordinal numbers in PHP
Bounded context DDD, folder structure with classes by DDD
Causes and solutions for the error - connect() to unix:/run/php-fpm/www.sock failed (Resource temporarily unavailable) while connecting to upstream)
Best practice using Dependency Injection for class with static methods in php
letsencrypt Certbot Error .plugins.selection: Selected authenticator None and installer None [solved]
The Evolution of Time Zones in PHP: What's Added, What's Removed, and Why — From PHP 5.6 to PHP 8
Difference between Entity, Domain Model, and DataModel in the context of DDD
PHP: History and Fundamentals of the Server-Side Language
What are the ways to organize batch data processing in PHP?
Authorization in Online Services. Policies and Gates in Laravel - Self-Check Test with Answers
OAuth 1 and 2 Authorization: Concept and Examples
How WebSocket works in Laravel: real-time applications using Echo / Reverb
Ways to create asynchronous responses (deferred processing) in plain PHP or Laravel (backend)
How to reduce the size of a Js Electron project?