PHP

What is PHP?

The acronym PHP initially stood for Personal Home Page. 

As of version 3, it stands for PHP Hypertext Preprocessor. It is a general purpose server side scripting language that is used to develop:

  • Dynamic Websites
  • Custom Web Portal (Like ERP, CRM)
  • Web Applications
  • E-commerce Websites (Like Flipkart, Amazon, Paytm, Snapdeal etc)
  • CMS – Content Management System

Importance of  PHP?

  • It costs low with cost effective database applications
  • It is platform independent
  • PHP supports all major web servers
  • The existence of multiple security layers make PHP one of the most secure options for developing the most critical websites and web applications.
  • PHP supports a wide array of databases including dataBase, MySQL etc.

History of PHP

  • Designed by Rasmus Lerdorf
  • Developer The PHP Development Team, Zend Technologies
  • First appeared June 8, 1995; 21 years ago
  • Stable release 7.1.0/ December 1, 2016

Basic Structure of PHP


<?php
//your code here
?>

Example:

<!doctype html>
 <html>
 <head><title>Hello World Script</title></head>
  <body>
  <?php
     echo "<p>Hello World!</p>";
   ?>
  </body>
 </html>

Printing statement in PHP

If you want to print/echo some string/variable or number in php

<?php 

$variable = "your string"; //

echo $variable; //

?>

File Extension of PHP

  • PHP files have the file extension .php

Comment Line in PHP

  • Single Line Comments

Single line comments start with //.

Any text between // and the end of the line will be ignored by PHP(will not be executed).

Example

echo 'This is a test'; // This is a one-line c++ style comment
  • Multi-line Comments

Multi-line comments start with /* and end with */.

Any text between /* and */ will be ignored by PHP.

Example

/* This is a multi line comment

          yet another line of comment */

/*  echo 'This is yet another test';

     echo 'Hi'; */

    echo 'One Final Test'; # This is a one-line shell-style comment

Variable Declaration

In PHP, a variable starts with the $ sign, followed by the name of the variable:

Example

<?php

$Vraiable_name = "Hello world!";

$x = 5;

$y = 10.5;

?>

A variable can have a short name (like x and y) or a more descriptive name (age, car name, total_volume).

Rules for PHP variables:

  • A variable starts with the $ sign, followed by the name of the variable
  • A variable name must start with a letter or the underscore character
  • A variable name cannot start with a number
  • A variable name can only contain alpha-numeric characters and underscores (A-z, 0-9, and _ )
  • Variable names are case-sensitive ($age and $AGE are two different variables)
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