Random Question - PHP

Question: How array_walk function works in PHP?
Purpose: It is used to update the elements/index of original array.
How: in array_walk, two parameter are required. 
1st: original array
2nd: An callback function, with use of we update the array.

How to find duplicate email records in users table?

SELECT u1.first_name, u1.last_name, u1.email FROM users as u1
INNER JOIN (
    SELECT email FROM users GROUP BY email HAVING count(id) > 1
    ) u2 ON u1.email = u2.email;

Question: How to pass data in header while using CURL?

$url='http://www.web-technology-experts-notes.in';
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 0);
curl_setopt($ch, CURLOPT_HTTPHEADER, array(
  'headerKey: HeaderValue ',
  'Content-Type: application/json',
  "HTTP_X_FORWARDED_FOR: xxx.xxx.x.xx"
));
echo curl_exec($ch);
curl_close($ch);

Question: How to pass JSON Data in CURL?

$url='http://www.web-technology-experts-notes.in';
$jsonData='{"name":"Web Technology Experts","email":"contact@web-technology-experts-notes.in"}';
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 0);
curl_setopt($ch, CURLOPT_POSTFIELDS, $jsonData);
curl_close($ch);

Question: What is Final Keyword in PHP?
PHP introduces the final keyword, which prevents child classes from overriding a method by prefixing the definition with final keyword.

Question: How can we prevent SQL-injection in PHP? Sanitize the user data before Storing in database.
While displaying the data in browser Convert all applicable characters to HTML entities using htmlentities functions.



Question: How to redirect https to http URL and vice versa in .htaccess?
Redirect https to http

RewriteEngine On
RewriteCond %{HTTPS} on
RewriteRule (.*) http://%{HTTP_HOST}%{REQUEST_URI} [R=301,L]

Redirect http to https

RewriteEngine on
RewriteCond %{HTTPS} off
RewriteRule ^(.*)$ https://%{HTTP_HOST}/$1 [R=301,L]

Question: What are benefits of htaccess?
We can do following benefits stuff with htaccess.
Routing the URL
Mange Error Pages for Better SEO
Redirection pages
Detect OS (like Mobile/Laptop/Ios/Android etc)
Set PHP Config variable
Set Environment variable
Allow/Deny visitors by IP Address
Password protection for File/Directory
Optimize Performance of website
Improve Site Security

Question: Difference between Apache and Nginx?
Nginx is based on event-driven architecture.
Apache is based on process-driven architecture. 

Nginx development started only in 2002. 
Apache initial release was in 1995.

Nginx doesn't create a new process for a new request.
Apache creates a new process for each request.

In Nginx, memory consumption is very low for serving static pages. 
Apache’s nature of creating new process for each request, that's why it  increases the memory consumption.

Nginx is extremely fast for serving static pages as compare to Apache.

In complex configurations apache can be configured easily as compare to Nginx.

Apache has excellent documentation as compare to Nginx. 

Nginx does not support Operating Systems like OpenVMS and IBMi where as Apache supports much wider range of Operating Systems. 

The performance and scalability of Nginx is not completely dependent on hardware resources.
The Performance and scalability of the Apache is dependent on underlying hardware resources like memory and CPU.