PHP
PHP is a powerful tool for making dynamic and interactive Web pages.PHP is
the widely-used, free, and efficient alternative to competitors such as
Microsoft's ASP.In our PHP tutorial you will learn about PHP, and how to execute
scripts on your server.PHP is a server-side scripting language.
What You Should Already Know?
Before you continue you should have a basic understanding of the following:
* HTML/XHTML * JavaScript
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 * PHP is free to download
and use
What is a PHP File?
* PHP files can 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 (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?
To get access to a web server with PHP support, you can:* Install Apache
(or IIS) on your own server, install PHP, and MySQL* Or find a web hosting plan
with PHP and MySQL support
What do you Need?
If your server supports PHP you don't need to do anything.*Just create some
.php files in your web directory, and the server will parse them for you.
Because it is free, most web hosts offer PHP support.However, *if your server
does not support PHP, you must install PHP.Here is a link to a good tutorial
from PHP.net on how to install PHP5: http://www.php.net/manual/en/install.php
Download PHP
PHP code is executed on the server, and the plain HTML result is sent to
the browser.
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 ?>.
For maximum compatibility, we recommend that you use the standard form
(<?php) rather than the shorthand form.
<?php
?>
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>
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".
Note: The file must have a .php
extension. If the file has a .html extension, the PHP code will not be
executed.
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 isa commentblock*/
?></body></html>
A variable is used to store information.
Variables in PHP
Variables are used for storing values, like text strings, numbers or
arrays.
When a variable is declared, it can be used over and over again in your
script.
All variables in PHP start with a $ sign symbol.
The correct way of declaring a variable in PHP: $var_name = value;
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
containing a string, and a variable containing a number:
<?php
$txt="Hello World!";
$x=16;
?> PHP is a Loosely
Typed Language *In PHP, a variable
does not need to be declared before adding a value to it.*In the example above,
you see that you do not have to tell PHP which data type the variable is.*PHP
automatically converts the variable to the correct data type, depending on its
value.*In a strongly typed programming language, you have to declare (define)
the type and name of the variable before using it.*In PHP, the variable is
declared automatically when you use it.
Naming Rules for Variables
* A variable name must start with a letter
or an underscore "_" * A
variable name can only contain alpha-numeric characters and underscores (a-z,
A-Z, 0-9, and _ ) * A variable name
should not contain spaces. If a variable name is more than one word, it should
be separated with an underscore ($my_string), or with capitalization
($myString)*A string variable is used to store and manipulate text.String
Variables in PHP*String variables are used for values that contain characters.
In this chapter we are going to look at the most
common functions and operators used to manipulate strings in PHP.
After we create a string we can manipulate it. A string can be used
directly in a function or it can be stored in a variable.Below, the PHP script
assigns the text "Hello World" to a string variable called $txt:
<?php
$txt="Hello World";
echo $txt;
?>
The output of the code above will be: Hello World
Now, lets try to use some different functions and operators to manipulate
the string.*The Concatenation Operator*There is only one string operator in
PHP.*The concatenation operator (.) is
used to put two string values together.*To concatenate two string variables
together, use the concatenation operator:
<?php
$txt1="Hello World!";
$txt2="What a nice day!";
echo $txt1 . " " . $txt2;
?>
The output of the code above will be: Hello World! What a nice day!
If we look at the code above you see that we used the concatenation
operator two times. This is because we had to insert a third string (a space
character), to separate the two strings.
The strlen() function ……………..The strlen() function is used
to return the length of a string.
Let's find the length of a string:
<?php
echo strlen("Hello world!");
?>
The output of the code above will be: 12
The length of a string is often used in loops or other functions, when it
is important to know when the string ends. (i.e. in a loop, we would want to
stop the loop after the last character in the string).
The strpos() function………The strpos() function is
used to search for a character/text within a string.If a match is found, this
function will return the character position of the first match. If no match is
found, it will return FALSE.Let's see if we can find the string
"world" in our string:
<?php
echo strpos("Hello world!","world");
?>
The output of the code above will be: 6
The position of the string "world" in the example above is 6. The
reason that it is 6 (and not 7), is that the first character position in the
string is 0, and not 1.
Complete PHP String Reference
For a complete reference of all string functions, go to our complete PHP
String Reference.*The reference contains a brief description, and examples of
use, for each function!*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
%= 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 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 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
the following conditional statements:* if statement - use this statement to
execute some code only if a specified condition is true* if...else statement -
use this statement to execute some code if a condition is true and another code
if the condition is false* if...elseif....else statement - use this statement
to select one of several blocks of code to be executed * switch statement - use
this statement to select one of many blocks of code to be executed
The if Statement………Use the if statement to execute
some code only if a specified condition is true.
Syntax
if (condition) code to be executed if condition is true;
The following example will output "Have a nice weekend!" if the
current day is Friday:
<html><body>
<?php
$d=date("D");
if ($d=="Fri") echo "Have a nice weekend!";
?></body></html>
Notice that there is no ..else.. in this syntax. The code is executed only
if the specified condition is true.
The if...else Statement
Use the if....else statement to execute some code if a condition is true
and another code if a condition is false.
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>
The if...elseif....else Statement
Use the if....elseif...else statement to select
one of several blocks of code to be executed.
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 ($d=="Sun")
echo "Have a nice
Sunday!";
else
echo "Have a nice
day!";
?></body></html>
Conditional statements are used to perform
different actions based on different conditions.
The PHP
Switch Statement…………………….Use the switch statement to select one of many blocks of code to
be executed. Syntax
switch (n)
{
case label1:
code to
be executed if n=label1;
break;
case label2:
code to
be executed if n=label2;
break;
default:
code to
be executed if n is different from both label1 and label2;
}
This is how it works: First we have a single expression n (most often a
variable), that is evaluated once. The value of the expression is then compared
with the values for each case in the structure. If there is a match, the block
of code associated with that case is executed. Use break to prevent the code
from running into the next case automatically. The default statement is used if
no match is found.
Example
<html><body>
<?php
switch ($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>
An array stores multiple values in one single
variable.
What is an Array?
A variable is a storage area holding a number or text. The problem is, a
variable will hold only one value.
An array is a special variable, which can store multiple values in one
single variable.
If you have a list of items (a list of car names, for example), storing the
cars in single variables could look like this:
$cars1="Saab";
$cars2="Volvo";
$cars3="BMW";
However, what if you want to loop through the cars and find a specific one?
And what if you had not 3 cars, but 300?*The best solution here is to use an
array!*An array can hold all your variable values under a single name. And you
can access the values by referring to the array name.*Each element in the array
has its own index so that it can be easily accessed.*In PHP, there are three
kind of arrays:
*
Numeric array - An array with a numeric index* 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 array element with a numeric index.There are two methods to create a numeric
array.
1. In the following example the index are
automatically assigned (the index starts at 0):
$cars=array("Saab","Volvo","BMW","Toyota");
2. In the following example we assign the index
manually:
$cars[0]="Saab";
$cars[1]="Volvo";
$cars[2]="BMW";
$cars[3]="Toyota";
Example
In the following example you access the variable values by referring to the
array name and index:
<?php
$cars[0]="Saab";
$cars[1]="Volvo";
$cars[2]="BMW";
$cars[3]="Toyota";
echo $cars[0] . " and " . $cars[1] . " are Swedish
cars.";
?>
The code above will output: Saab and Volvo are Swedish cars.
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);
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: Peter is 32 years old.
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?
Complete PHP Array Reference
For a complete reference of all array functions, go to our complete PHP
Array Reference.*The reference contains a brief description, and examples of
use, for each function!Loops execute a block of code a specified number of
times, or while a specified condition is true.
PHP Loops
Often when you write code, you want the same block of code to run over and
over again in a row. Instead of adding several almost equal lines in a script
we can use loops to perform a task like this.
In PHP, we have the following looping statements:
* while - loops through a block of code while a specified condition is true*
do...while - loops through a block of code once, and then repeats the loop
as long as a 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
The while Loop
The while loop executes a block of code while a
condition is true.
Syntax: while
(condition)
{
code to be executed;
}
Example............The example below defines a loop that starts with i=1. The loop will
continue to run as long as i is less than, or equal to 5. i will increase by 1
each time the loop runs:
<html><body>
<?php
$i=1;
while($i<=5)
{
echo
"The number is " . $i . "<br />";
$i++;
?> </body></html>
Output:
The number is 1
The number is 2
The number is 3
The number is 4
The number is 5
The do...while Statement
The do...while statement will always execute the block of code once, it
will then check the condition, and repeat the loop while the condition is true.
Syntax
do
{
code to
be executed;
}
while (condition);
Example............The example below defines a loop that starts with i=1. It will then
increment i with 1, and write some output. Then the condition is checked, and
the loop will continue to run as long as i is less than, or equal to 5:
<html> <body> <?php
$i=1;
do
{
$i++;
echo "The number is " .
$i . "<br />";
}
while ($i<=5);
?> </body> </html>
Output:
The number is 2
The number is 3
The number is 4
The number is 5
The number is 6
The for loop and the foreach loop will be
explained in the next chapter.
Loops execute a block of code a specified number of times, or while a
specified condition is true.The for Loop
The for loop is used when you know in advance how
many times the script should run.
Syntax
for (init; condition; increment)
{
code to
be executed;
}
Parameters: * init: Mostly used to set a
counter (but can be any code to be executed once at the beginning of the loop)*
condition: Evaluated for each loop iteration. If it evaluates to TRUE, the loop
continues. If it evaluates to FALSE, the loop ends.* increment: Mostly used to
increment a counter (but can be any code to be executed at the end of the loop)Note: Each of the parameters
above can be empty, or have multiple expressions (separated by commas).
Example
The example below defines a loop that starts with i=1. The loop will
continue to run as long as i is less than, or equal to 5. i will increase by 1
each time the loop runs:
<html><body>
<?php
for ($i=1; $i<=5; $i++)
{
echo "The number is " .
$i . "<br />";
}
?></body></html>
Output:
The number is 1
The number is 2
The number is 3
The number is 4
The number is 5
The foreach Loop
The foreach loop is used to loop through arrays.
Syntax
foreach ($array as $value)
{
code to be executed;
}
For every loop iteration, the value of the
current array element is assigned to $value (and the array pointer is moved by
one) - so on the next loop iteration, you'll be looking at the next array
value.
Example The following example
demonstrates a loop that will print the values of the given array:
<html><body> <?php
$x=array("one","two","three");
foreach ($x as $value)
{
echo $value . "<br
/>";
}
?></body></html>
Output:
One
two
three
The real power of PHP comes from its functions.
In PHP, there are more than 700 built-in functions. PHP Built-in Functions
For a complete reference and examples of the built-in functions, please
visit our PHP Reference.
PHP Functions In this chapter we will show you how to create
your own functions.
To keep the script from being executed when the page loads, you can put it
into a function.
A function will be executed by a call to the function.You may call a function
from anywhere within a page.
Create a PHP Function A function will be executed by a call
to the function.
Syntax
function functionName()
{
code to be executed;
}
PHP function guidelines: * Give the function a name that reflects what
the function does * The function name can start with a letter or underscore
(not a number) Example
A simple function that writes my name when it is
called:
<html><body><?php
function writeName()
{
echo "Kai Jim Refsnes";
}
echo "My name is ";
writeName();
?></body></html>
Output:
My name is Kai Jim Refsnes
PHP Functions - Adding parameters
To add more functionality to a function, we can add parameters. A parameter
is just like a variable.
Parameters are specified after the function name, inside the parentheses.
Example 1
The following example will write different first names, but equal last
name:
<html><body><?php
function writeName($fname)
{
echo $fname . " Refsnes.<br />";
}
echo "My name is ";
writeName("Kai Jim");
echo "My sister's name is ";
writeName("Hege");
echo "My brother's name is ";
writeName("Stale");
?></body></html> Output:
My name is Kai Jim Refsnes.
My sister's name is Hege Refsnes.
My brother's name is Stale Refsnes.
Example 2
The following function has two parameters:
<html><body><?php
function writeName($fname,$punctuation)
{
echo $fname . " Refsnes" . $punctuation . "<br
/>";
}
echo "My name is ";
writeName("Kai Jim",".");
echo "My sister's name is ";
writeName("Hege","!");
echo "My brother's name is ";
writeName("Ståle","?");
?></body></html> Output:
My name is Kai Jim Refsnes.
My sister's name is Hege Refsnes!
My brother's name is Ståle Refsnes?
PHP Functions - Return values
To let a function return a value, use the return statement.
Example
<html><body><?php
function add($x,$y)
{
$total=$x+$y;
return $total;
}
echo "1 + 16 = " . add(1,16);
?></body></html>
Output:
1 + 16 = 17
The PHP $_GET and $_POST
variables are used to retrieve information from forms, like user input.
PHP Form Handling
The most important thing to notice when dealing with HTML forms and PHP is
that any form element in an HTML page will automatically be available to your
PHP scripts.
Example
The example below contains an HTML form with two input fields and a submit
button:
<html><body>
<form action="welcome.php" method="post">
Name: <input type="text" name="fname" />
Age: <input type="text" name="age" />
<input type="submit" />
</form></body></html>
When a user fills out the form above and click on the submit button, the
form data is sent to a PHP file, called "welcome.php":
"welcome.php" looks like this:
<html><body>
Welcome <?php echo $_POST["fname"]; ?>!<br />
You are <?php echo $_POST["age"]; ?> years old.
</body></html>
Output could be something like this:
Welcome John!
You are 28 years old.
The PHP $_GET and $_POST
variables will be explained in the next chapters.
Form Validation
User input should be validated on the browser whenever possible (by client
scripts). Browser validation is faster and reduces the server load.*
You should consider server validation if the user input will be inserted
into a database. A good way to validate a form on the server is to post the
form to itself, instead of jumping to a different page. The user will then get
the error messages on the same page as the form. This makes it easier to
discover the error.*In PHP, the predefined $_GET variable is used to collect
values in a form with method="get".
The $_GET Variable
The predefined $_GET variable is used to collect values in a form with
method="get"
Information sent from a form with the GET method is visible to everyone (it
will be displayed in the browser's address bar) and has limits on the amount of
information to send. Example
<form action="welcome.php" method="get">
Name: <input type="text" name="fname" />
Age: <input type="text" name="age" />
<input type="submit" />
</form>
When the user clicks the "Submit" button, the URL sent to the
server could look something like this:
The "welcome.php" file can now use the $_GET variable to collect
form data (the names of the form fields will automatically be the keys in the
$_GET array):
Welcome <?php echo $_GET["fname"]; ?>.<br />
You are <?php echo $_GET["age"]; ?> years old!
When to use method="get"?
When using method="get" in HTML forms, all variable names and
values are displayed in the URL.
Note: This method should not be used when sending passwords or other sensitive
information!
However, because the variables are displayed in the URL, it is possible to
bookmark the page.
This can be useful in some cases.
Note: The get method is not suitable for very large variable values. It should
not be used with values exceeding 2000 characters.*In PHP, the predefined $_POST variable is used to collect values in
a form with method="post".
The $_POST Variable
The predefined $_POST variable is used to collect values from a form sent
with method="post".
Information sent from a form with the POST method is invisible to others
and has no limits on the amount of information to send.
Note: However, there is an 8 Mb max size for the POST method, by default (can be
changed by setting the post_max_size in the php.ini file). Example
<form action="welcome.php" method="post">
Name: <input type="text" name="fname" />
Age: <input type="text" name="age" />
<input type="submit" />
</form>
When the user clicks the "Submit" button, the URL will look like
this:
The "welcome.php" file can now use the $_POST variable to collect
form data (the names of the form fields will automatically be the keys in the
$_POST array):
Welcome <?php echo $_POST["fname"]; ?>!<br />
You are <?php echo $_POST["age"]; ?> years old.
When to use method="post"?
Information sent from a form with the POST method is invisible to others
and has no limits on the amount of information to send.*However, because the
variables are not displayed in the URL, it is not possible to bookmark the
page. The PHP $_REQUEST Variable
The predefined $_REQUEST variable contains the contents of both $_GET,
$_POST, and $_COOKIE.
The $_REQUEST variable can be used to collect form data sent with both the
GET and POST methods.
Example
Welcome <?php echo $_REQUEST["fname"]; ?>!<br />
You are <?php echo $_REQUEST["age"]; ?> years old.
PHP Date() Function
The PHP date() function is used to format a time and/or date.
The PHP Date() Function
The PHP date() function formats a timestamp to a more readable date and
time.
Tip A timestamp is a sequence of characters, denoting the date and/or time
at which a certain event occurred.
Syntax
date(format,timestamp)
Parameter Description
format Required. Specifies the format
of the timestamp
timestamp Optional. Specifies
a timestamp. Default is the current date and time
PHP Date() - Format the Date
The required format parameter in the date() function specifies how to
format the date/time.
Here are some characters that can be used:* d - Represents the day of the
month (01 to 31)
* m - Represents a month (01 to
12) * Y - Represents a year (in four
digits)
A list of all the characters that can be used in the format parameter, can
be found in our PHP Date reference.*Other characters, like"/",
".", or "-" can also be inserted between the letters to add
additional formatting:
<?php
echo date("Y/m/d") . "<br />";
echo date("Y.m.d") . "<br />";
echo date("Y-m-d");
?>
The output of the code above could be something
like this:
2009/05/11
2009.05.11 2009-05-11
PHP Date() - Adding a Timestamp
The optional timestamp parameter in the date() function specifies a
timestamp. If you do not specify a timestamp, the current date and time will be
used.
The mktime() function returns the Unix timestamp for a date.
The Unix timestamp contains the number of seconds between the Unix Epoch
(January 1 1970 00:00:00 GMT) and the time specified.
Syntax for mktime()
mktime(hour,minute,second,month,day,year,is_dst)
To go one day in the future we simply add one to the day argument of
mktime():
<?php
$tomorrow =
mktime(0,0,0,date("m"),date("d")+1,date("Y"));
echo "Tomorrow is ".date("Y/m/d", $tomorrow);
?>
The output of the code above could be something
like this:
Tomorrow is 2009/05/12 Complete
PHP Date Reference
For a complete reference of all date functions, go to our complete PHP Date
Reference.
The reference contains a brief description, and examples of use, for each
function!
