Php Constants are name or identifier which cannot be modified Throughout the execution of a program

Php constants can be defined by 2 ways:

• Using define function
• Using Const keyword

A comment in PHP code is a line that is not executed as a part of a program

It's purpose is to be Read By someone who is looking at the code There Are two type of Comments in PHP

• Single-Line
• MultiLine

<?php
    // This is Single-line comment
    # Is is also a Single-line comment
?>

<?php 
/* This is a Multi-line Comment
that can comment multiple 
Lines */ 
?>

Just like other Programmign language , PHP also supports various types of Operations like Arithmetic Operation, Logical Operations ,Increment/Decrement Operation ,etc

Array is a Compound Data Type That hold multiple values of similar type in a single Variable

• Indexed Array
• Associative Array
• Multidimensional Array

• Less Code: We Don't need to define Multiple variables.
• Easy to Traverse: With a single loop we cal traverse all the element of an array
• Sorting: We can sort the array

Array Functions

In Any Programming Languages , Control structures are specific commands which are used to control the Logical flow of the Program during its execution.

• Condition Control Statement
• Looping Control Statement

In simple way ,A Regular Expression Is a way to do pattern matching . A regular Expression is a string that represents a pattern.

It is Commonly Known as "Regex" or "RegExp"

• Matching
• Substituting
• Splitting

Some predefined Variables in PHP are "SuperGlobals",which means that they are always accessible , regardless of scope and you can access them from any function , class or file without having to do anything special.

ex - $GLOBALS , $_GET , $_POST

A function is a piece of code in a larger program . The function performs a specific task

• Reducing duplication of code
• Decomposing complex problems into simpler pieces
• Imporving clarity of the code
• Reuse of code

• Built-in Functions
• User Defined Functions

The scope of a variable is defined as its range in the program under which it can be accessed. In other words, "The scope of a variable is the portion of the program within which it is defined and can be accessed."

• Local Variable
• Global Variable
• Static variable

PHP makes use of mail() To send an email.

mail(to,subject,message,header,parameters);

HTTP is a stateless protocol which means every user request is processed before it . Hence there is no way to store or send any user specific details using HTTP protocol.

PHP allows us to save certain states of the application either on the server itself, or in the user's browser . In form of Session and Cookies

File Handling is an important part of web application. We often need to open and process a file for different tasks. PHP has several functions for creating , reading , [uploading] , and editing files Ex - fopen() , fwrite() , fclose()

We can include the content of a PHP file into another PHP file before the server executes it . There are two PHP function which can be used to include one PHP file into another File.

• The Include() function
• The Require() function

Procedural programming is about writing procedures or functions that perform operations on the data , while object-oriented programming is about creating objects that contain both data and functions.

Object oriented programming had several advantages over procedural programming

• It is Faster
• It provides a Clear Structure for the Programs
• It helps to Keep the PHP code "DRY: Don't Repeat Yourself", and makes the code easier to maintain , modify and debug
• It ensures that the created code is fully reusable with less code and shorter time