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Beginners Guide to PHP

P H P

What is PHP?

PHP stands for PHP: Hypertext Preprocessor
PHP is a server-side scripting language, like ASP
PHP scripts are executed on the server
PHP supports many databases (MySQL, Informix, Oracle, Sybase, Solid, PostgreSQL, Generic ODBC, etc.)
PHP is an open source software (OSS)
PHP is free to download and use

What is a PHP File?

PHP files may contain text, HTML tags and scripts
PHP files are returned to the browser as plain HTML
PHP files have a file extension of ".php", ".php3", or ".phtml"

What is MySQL?

MySQL is a small database server
MySQL is ideal for small and medium applications
MySQL supports standard SQL
MySQL compiles on a number of platforms
MySQL is free to download and use

PHP + MySQL

PHP combined with MySQL are cross-platform (means that you can develop in Windows and serve on a Unix platform)

Why PHP?

PHP runs on different platforms (Windows, Linux, Unix, etc.)
PHP is compatible with almost all servers used today (Apache, IIS, etc.)
PHP is FREE to download from the official PHP resource: www.php.net
PHP is easy to learn and runs efficiently on the server side

Where to Start?

Install an Apache server on a Windows or Linux machine
Install PHP on a Windows or Linux machine
Install MySQL on a Windows or Linux machine

You cannot view the PHP source code by selecting "View source" in the browser - you will only see the output from the PHP file, which is plain HTML. This is because the scripts are executed on the server before the result is sent back to the browser.

Basic PHP Syntax

A PHP file normally contains HTML tags, just like an HTML file, and some PHP scripting code.

Below, we have an example of a simple PHP script which sends the text "Hello World" to the browser:

<html>

<body>

<?php echo "Hello World"; ?>

</body>

</html>

A PHP scripting block always starts with <?php and ends with ?>. A PHP scripting block can be placed anywhere in the document.

Each code line in PHP must end with a semicolon. The semicolon is a separator and is used to distinguish one set of instructions from another.

There are two basic statements to output text with PHP: echo and print. In the example above we have used the echo statement to output the text "Hello World".

Variables in PHP

All variables in PHP start with a $ sign symbol. Variables may contain strings, numbers, or arrays.

Below, the PHP script assigns the string "Hello World" to a variable called $txt:

<html>

<body>

<?php

$txt="Hello World";

echo $txt;

</body>

</html>

To concatenate two or more variables together, use the dot (.) operator:

<html>

<body>

<?php

$txt1="Hello World";

$txt2="1234";

echo $txt1 . " " . $txt2 ;

</body>

</html>

The output of the script above will be: "Hello World 1234".

Comments in PHP

In PHP, we use // to make a single-line comment or /* and */ to make a large comment block.

<html>

<body>

<?php

//This is a comment

This is

a comment

block

</body>

</html>

Operators are used to operate on values.

PHP Operators

This section lists the different operators used in PHP.

Arithmetic Operators

Operator	Description	Example	Result
+	Addition	x=2 x+2	4
-	Subtraction	x=2 5-x	3
*	Multiplication	x=4 x*5	20
/	Division	15/5 5/2	3 2.5
%	Modulus (division remainder)	5%2 10%8 10%2	1 2 0
++	Increment	x=5 x++	x=6
--	Decrement	x=5 x--	x=4

Assignment Operators

Operator	Example	Is The Same As
=	x=y	x=y
+=	x+=y	x=x+y
-=	x-=y	x=x-y
*=	x*=y	x=x*y
/=	x/=y	x=x/y
%=	x%=y	x=x%y

Comparison Operators

Operator	Description	Example
==	is equal to	5==8 returns false
!=	is not equal	5!=8 returns true
>	is greater than	5>8 returns false
<	is less than	5<8 returns true
>=	is greater than or equal to	5>=8 returns false
<=	is less than or equal to	5<=8 returns true

Logical Operators

Operator	Description	Example
&&	and	x=6 y=3 (x < 10 && y > 1) returns true
\|\|	or	x=6 y=3 (x==5 \|\| y==5) returns false
!	not	x=6 y=3 !(x==y) returns true

Conditional statements in PHP are used to perform different actions based on different conditions.

Conditional Statements

Very often when you write code, you want to perform different actions for different decisions. You can use conditional statements in your code to do this.

In PHP we have two conditional statements:

if (...else) statement - use this statement if you want to execute a set of code when a condition is true (and another if the condition is not true)
switch statement - use this statement if you want to select one of many sets of lines to execute

The If Statement

If you want to execute some code if a condition is true and another code if a condition is false, use the if....else statement.

Syntax

if (condition)

code to be executed if condition is true;

else

code to be executed if condition is false;

Example

The following example will output "Have a nice weekend!" if the current day is Friday, otherwise it will output "Have a nice day!":

<html>

<body>

<?php

$d=date("D");

if ($d=="Fri")

echo "Have a nice weekend!";

else

echo "Have a nice day!";

</body>

</html>

If more than one line should be executed when a condition is true, the lines should be enclosed within curly braces:

<html>

<body>

<?php

$x=10;

if ($x==10)

{

echo "Hello<br />";

echo "Good morning<br />";

}

</body>

</html>

The Switch Statement

If you want to select one of many blocks of code to be executed, use the Switch statement.

Syntax

switch (expression)

{

case label1:

code to be executed if expression = label1;

break;

case label2:

code to be executed if expression = label2;

break;

default:

code to be executed

if expression is different

from both label1 and label2;

}

Example

This is how it works: First we have a single expression (most often a variable), that is evaluated once. The value of the expression is then compared with the values for each case in the structure. If there is a match, the block of code associated with that case is executed. Use break to prevent the code from running into the next case automatically. The default statement is used if none of the cases are true.

<html>

<body>

<?php

switch ($x)

{

case 1:

echo "Number 1";

break;

case 2:

echo "Number 2";

break;

case 3:

echo "Number 3";

break;

default:

echo "No number between 1 and 3";

}

</body>

</html>