What You Should Already Know
Before you continue you should have a basic understanding of the following:
- HTML / XHTML
- Some scripting knowledge
If you want to study these subjects first, find the tutorials on our Home page.
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 database server
- MySQL is ideal for both small and large 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
What do You Need?
This tutorial will not explain how to install PHP, MySQL, or Apache Server.
If your server supports PHP - you don't need to do anything! You do not need to compile anything or install any extra tools - just create some .php files in your web directory - and the server will parse them for you. Most web hosts offer PHP support.
However, if your server does not support PHP, you must install PHP. Below is a link to a good tutorial from PHP.net on how to install PHP5:
Download PHP
Download MySQL Database
Download Apache Server
Basic PHP Syntax
A PHP scripting block always starts with <?php and ends with ?>. A PHP scripting block can be placed anywhere in the document.
On servers with shorthand support enabled you can start a scripting block with <? and end with ?>.
However, for maximum compatibility, we recommend that you use the standard form (<?php) rather than the shorthand form.
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>
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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".
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>
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Variables in PHP
Variables are used for storing a values, like text strings, numbers or arrays.
When a variable is set it can be used over and over again in your script
All variables in PHP start with a $ sign symbol.
The correct way of setting a variable in PHP:
New PHP programmers often forget the $ sign at the beginning of the variable. In that case it will not work.
Let's try creating a variable with a string, and a variable with a number:
<?php
$txt = "Hello World!";
$number = 16;
?>
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PHP is a Loosely Typed Language
In PHP a variable does not need to be declared before being set.
In the example above, you see that you do not have to tell PHP which data type the variable is.
PHP automatically converts the variable to the correct data type, depending on how they are set.
In a strongly typed programming language, you have to declare (define) the type and name of the variable before using it.
In PHP the variable is declared automatically when you use it.
Variable Naming Rules
- A variable name must start with a letter or an underscore "_"
- A variable name can only contain alpha-numeric characters and underscores (a-Z, 0-9, and _ )
- A variable name should not contain spaces. If a variable name is more than one word, it should be separated with underscore ($my_string), or with capitalization ($myString)
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
|
|
%=
|
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
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.
- 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
- elseif statement - is used with the if...else statement to execute a set of code if one of several condition are true
The If...Else 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 if a condition is true/false, the lines should be enclosed within curly braces:
<html>
<body>
<?php
$d=date("D");
if ($d=="Fri")
{
echo "Hello!<br />";
echo "Have a nice weekend!";
echo "See you on Monday!";
}
?>
</body>
</html>
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The ElseIf Statement
If you want to execute some code if one of several conditions are true use the elseif statement
Syntax
if (condition)
code to be executed if condition is true;
elseif (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, and "Have a nice Sunday!" if the current day is Sunday. Otherwise it will output "Have a nice day!":
<html>
<body>
<?php
$d=date("D");
if ($d=="Fri")
echo "Have a nice weekend!";
elseif ($d=="Sun")
echo "Have a nice Sunday!";
else
echo "Have a nice day!";
?>
</body>
</html>
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The Switch Statement
If you want to select one of many blocks of code to be executed, use the Switch statement.
The switch statement is used to avoid long blocks of if..elseif..else code.
Syntax
switch (expression)
{
case label1:
code to be executed if expression = label1;
break;
case label2:
code to be executed if expression = label2;
break;
default:
code to be executed
if expression is different
from both label1 and label2;
}
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Example
This is how it works:
- A single expression (most often a variable) is evaluated once
- The value of the expression is compared with the values for each case in the structure
- If there is a match, the code associated with that case is executed
- After a code is executed, break is used to stop the code from running into the next case
- The default statement is used if none of the cases are true
<html>
<body>
<?php
switch ($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>
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What is an array?
When working with PHP, sooner or later, you might want to create many similar variables.
Instead of having many similar variables, you can store the data as elements in an array.
Each element in the array has its own ID so that it can be easily accessed.
There are three different kind of arrays:
- Numeric array - An array with a numeric ID key
- Associative array - An array where each ID key is associated with a value
- Multidimensional array - An array containing one or more arrays
Numeric Arrays
A numeric array stores each element with a numeric ID key.
There are different ways to create a numeric array.
Example 1
In this example the ID key is automatically assigned:
$names = array("Peter","Quagmire","Joe");
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Example 2
In this example we assign the ID key manually:
$names[0] = "Peter";
$names[1] = "Quagmire";
$names[2] = "Joe";
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The ID keys can be used in a script:
<?php
$names[0] = "Peter";
$names[1] = "Quagmire";
$names[2] = "Joe";
echo $names[1] . " and " . $names[2] .
" are ". $names[0] . "'s neighbors";
?>
|
The code above will output:
Quagmire and Joe are Peter's neighbors
|
Associative Arrays
An associative array, each ID key is associated with a value.
When storing data about specific named values, a numerical array is not always the best way to do it.
With associative arrays we can use the values as keys and assign values to them.
Example 1
In this example we use an array to assign ages to the different persons:
$ages = array("Peter"=>32, "Quagmire"=>30, "Joe"=>34);
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Example 2
This example is the same as example 1, but shows a different way of creating the array:
$ages['Peter'] = "32";
$ages['Quagmire'] = "30";
$ages['Joe'] = "34";
|
The ID keys can be used in a script:
<?php
$ages['Peter'] = "32";
$ages['Quagmire'] = "30";
$ages['Joe'] = "34";
echo "Peter is " . $ages['Peter'] . " years old.";
?>
|
The code above will output:
Multidimensional Arrays
In a multidimensional array, each element in the main array can also be an array. And each element in the sub-array can be an array, and so on.
Example
In this example we create a multidimensional array, with automatically assigned ID keys:
$families = array
(
"Griffin"=>array
(
"Peter",
"Lois",
"Megan"
),
"Quagmire"=>array
(
"Glenn"
),
"Brown"=>array
(
"Cleveland",
"Loretta",
"Junior"
)
);
|
The array above would look like this if written to the output:
Array
(
[Griffin] => Array
(
[0] => Peter
[1] => Lois
[2] => Megan
)
[Quagmire] => Array
(
[0] => Glenn
)
[Brown] => Array
(
[0] => Cleveland
[1] => Loretta
[2] => Junior
)
)
|
Example 2
Lets try displaying a single value from the array above:
echo "Is " . $families['Griffin'][2] .
" a part of the Griffin family?";
|
The code above will output:
Is Megan a part of the Griffin family?
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