UNIT 1 ----PHP LANGUAGE STRUCUTURE

THE STRUCTURE OF A PHP 

<?php

echo "<p>Hello World!</p>";

 ?>

•The PHP tags enclose only one statement

  an echo statement. 

•The echo statement is a PHP statement that you’ll use frequently.

•The output is simply the text that’s included between the double quotes.

BUILDING BLOCK OF PHP

žPHP supports a number of fundamental basic

data types, such as integers, floats, and strings.

Basic data types are the simplest building

blocks of a program.

žNote: PHP statements end with a semicolon (;).

   

BASIC PHP SYNTAX

—A PHP script can be placed anywhere in the

document. A PHP script starts with 

<?php 

and

ends with ?>:

?php

// PHP code goes here

?>

—The default file extension for PHP files is ".php".

COMMENTS IN PHP

—A comment in PHP code is a line that is not read/executed as part of the program. 

   Its only purpose is to be read by someone who is looking at the code.

Example: // PHP code goes here

Comments can be used to:

—Let others understand what you are doing.

—Remind yourself of what you did.

PHP CASE SENSITIVITY

—In PHP, NO keywords, classes, functions, and user-defined functions are case-sensitive.

—All three echo statements below are legal 

Example

                <?php
                       ECHO "Hello World!<br>";
                       echo "Hello World!<br>";
                       EcHo "Hello World!<br>";
            ?>

PHP VARIABLES

—Variables are "containers" for storing information. 

A variable can have a short name or a more descriptive name.

Example

               <?php
                 $txt = "Hello world!";
                 $x = 5;
                 $y = 10.5;
           ?>

RULES FOR PHP VARIABLES:

1.A variable starts with the $ sign, followed by the name of the

variable

2. A variable name must start with a letter or the underscore

character

3. A variable name cannot start with a number

4. A variable name can only contain alpha-numeric characters and

underscores (A-z, 0-9, and _ )

5. Variable names are case-sensitive ($age and $AGE are two

different variables).

Output Variables:

The PHP echo statement is often used to output data to the screen.

Ex:

       <?php      

             $txt = "W3Schools.com";
     echo "I love $txt!";             

           ?>


PHP VARIABLES SCOPE

žThe scope of a variable is the part of the script where the variable can be referenced/used.

žPHP has three different variable scopes:

                  1. local

                  2. global

                  3. static

PHP ECHO AND PRINT STATEMENTS

Echo and print are more or less the same. They are both used to output data to the screen.

Echo

žecho has no return value.

žecho can take multiple parameters.

Print

žprint has a return value of 1.

žprint can take one argument.

Note: echo is marginally faster than print.

PHP DATA TYPE

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

1.String

A string is a sequence of characters

     Ex:

   $x = "Hello world!";

              $y = 'Hello world!';

2. Integer

An integer data type is a non-decimal number between -2,147,483,648 and 2,147,483,647.

     Ex:  

   <?php
         $x = 5985;
         var_dump($x);
         ?>

3. Float

—Is a number with a decimal point or a number in exponential form.

—Ex:   

— $x = 10.365;

4. Boolean

—A Boolean represents two possible states:

TRUE or FALSE.

Ex: 

          $x = true;
        $y = false;

5. Array

   An array stores multiple values in one single

variable.

Ex:     

  $cars = array("Volvo","BMW","Toyota");

6. Object

An object is a data type which stores data and information on how to process that data. 

Ex:      

   $herbie = new Car();

7. NULL Value

—Null is a special data type whichcan have only one value: NULL.

Ex: 

        $x = null;

8. Resource

—The special resource type is not an  actual data type.

 It is the storing of a reference functions and resources external to PHP.

PHP CONSTANTS

—Constants are like variables except that once they are defined they cannot be changed or undefined.

—A valid constant name starts with a letter or underscore(no $sign before the constant name).

— To create a constant, the define() function.

—Syntax:

   define(name, value, case-insensitive)

Ex:

    define("GREETING", "Welcome to PHP!");
      echo GREETING;

PHP OPERATORS

 Operators are used to perform operations on

variables and values.

žArithmetic operators -> to perform arithmetical operations

žAssignment operators -> to write a value to a variable.

žComparison operators ->to compare two values

žIncrement/Decrement operators -> to increment or decrement  a variable's value.

žLogical operators -> to combine conditional statements.

žString operators -> specially designed for strings.

žArray operators -> to compare arrays.