PHP

What is PHP?

• PHP is an acronym for "PHP: Hypertext Preprocessor"
• PHP is a widely-used, open source scripting language
• PHP scripts are executed on the server
• PHP is free to download and use.

What Can PHP Do?

• PHP can generate dynamic page content
• PHP can create, open, read, write, delete, and close files on the server
• PHP can collect form data
• PHP can send and receive cookies
• PHP can add, delete, modify data in your database
• PHP can be used to control user-access
• PHP can encrypt data

PHP Data Types

Variables can store data of different types, and different data types can do different things.

PHP supports the following data types:

• String = (A string is a sequence of characters, like "Hello world!".)
• Integer  = ( An integer data type is a non-decimal number between -2,147,483,648 and 2,147,483,647.)
• Float = (floating point numbers - also called double)  = (A float (floating point number) is a number with a decimal point or a number in exponential form.)
• Boolean  = (A Boolean represents two possible states: TRUE or FALSE.)
• Array  =  (An array stores multiple values in one single variable.)
• Object = (An object is a data type which stores data and information on how to process that data.)
• NULL  = (Null is a special data type which can have only one value: NULL.
  A variable of data type NULL is a variable that has no value assigned to it.)
• Resource  = (The special resource type is not an actual data type. It is the storing of a reference to functions and resources external to PHP.)

        

PHP Operators

Operators are used to perform operations on variables and values.

PHP divides the operators in the following groups:

• Arithmetic operators  = (The PHP arithmetic operators are used with numeric values to perform common arithmetical operations, such as addition, subtraction, multiplication etc.)
• Assignment operators  = (The PHP assignment operators are used with numeric values to write a value to a variable.)
• Comparison operators  =  (The PHP comparison operators are used to compare two values (number or string):)
• Increment/Decrement operators  =  (The PHP increment operators are used to increment a variable's value.
  The PHP decrement operators are used to decrement a variable's value.)
• Logical operators  =  (The PHP logical operators are used to combine conditional statements.)
• String operators  =  (PHP has two operators that are specially designed for strings.)
• Array operators  =  (The PHP array operators are used to compare arrays.)
• Conditional assignment operators  =  (The PHP conditional assignment operators are used to set a value depending on conditions:)

  

PHP Loops

Loops are used to execute the same block of code again and again, as long as a certain condition is true.

In PHP, we have the following loop types:

• while -( loops through a block of code as long as the specified condition is true)
• do...while - loops through a block of code once, and then repeats the loop as long as the specified condition is true
• for - loops through a block of code a specified number of times
• foreach - loops through a block of code for each element in an array

PHP Global Variables - Superglobals

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.

The PHP superglobal variables are:

• $GLOBALS   = ($GLOBALS is a PHP super global variable which is used to access global variables from anywhere in the PHP script (also from within functions or methods).)
• $_SERVER  = ($_SERVER is a PHP super global variable which holds information about headers, paths, and script locations.)
• $_REQUEST = (PHP $_REQUEST is a PHP super global variable which is used to collect data after submitting an HTML form.)
• $_POST  =  (PHP $_POST is a PHP super global variable which is used to collect form data after submitting an HTML form with method="post". $_POST is also widely used to pass variables.)
• $_GET  =  (PHP $_GET is a PHP super global variable which is used to collect form data after submitting an HTML form with method="get".
  $_GET can also collect data sent in the URL.)
• $_FILES  
• $_ENV
• $_COOKIE
• $_SESSION

What is a Cookie?

=> A cookie is often used to identify a user. A cookie is a small file that the server embeds on the user's computer. Each time the same computer requests a page with a browser, it will send the cookie too. With PHP, you can both create and retrieve cookie values.(A cookie is created with the setcookie() function.)

What is a PHP Session?

=> A session is a way to store information (in variables) to be used across multiple pages. So; Session variables hold information about one single user, and are available to all pages in one application.

(A session is started with the session_start() function.)

What is JSON?

JSON stands for JavaScript Object Notation, and is a syntax for storing and exchanging data.

Since the JSON format is a text-based format, it can easily be sent to and from a server, and used as a data format by any programming language.

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PHP and JSON

PHP has some built-in functions to handle JSON.

First, we will look at the following two functions:

• json_encode()  
• json_decode()..........