PHP Tutorial
PHP is a powerful server-side
scripting language for creating dynamic and interactive websites.
PHP is the widely-used, free, and
efficient alternative to competitors such as Microsoft's ASP. PHP is perfectly
suited for Web development and can be embedded directly into the HTML code.
The PHP syntax is very similar to
Perl and C. PHP is often used together with Apache (web server) on various
operating systems. It also supports ISAPI and can be used with Microsoft's IIS
on Windows.
Introduction to PHP
A PHP file may contain text, HTML
tags and scripts. Scripts in a PHP file are executed on the server.
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
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
PHP Installation
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 PHP for free here: http://www.php.net/downloads.php
Download MySQL Database
Download MySQL for free here: http://www.mysql.com/downloads/index.html
Download Apache Server
Download Apache for free here: http://httpd.apache.org/download.cgi
PHP Syntax
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 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.
<?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".
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>
|
PHP Variables
Variables are used for storing
values, such as numbers, strings or function results, so that they can be used
many times in a script.
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:
$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 with a string, and a variable with a
number:
<?php
$txt = "Hello World!";
$number = 16;
?>
|
PHP is a Loosely Typed Language
In PHP a variable does not need to be declared before being set.
In the example above, you see that you do not have to tell PHP
which data type the variable is.
PHP automatically converts the variable to the correct data type,
depending on how they are set.
In a strongly typed programming language, you have to declare
(define) the type and name of the variable before using it.
In PHP the variable is declared automatically when you use it.
Variable Naming Rules
- A variable name must start with a letter or an underscore "_"
- A variable name can only contain alpha-numeric characters and underscores (a-Z, 0-9, and _ )
- A variable name should not contain spaces. If a variable name is more than one word, it should be separated with underscore ($my_string), or with capitalization ($myString)
PHP String
A string variable is used to store
and manipulate a piece of text.
Strings in PHP
String variables are used for a value that contains character
strings.
In this tutorial we are going to look at some of 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 string "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 our 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 variables together, use the dot (.) operator:
<?php
$txt1="Hello World";
$txt2="1234";
echo $txt1 . " " . $txt2;
?>
|
The output of the code above will be:
Hello World 1234
|
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.
Between the two string variables we added a string with a single
character, an empty space, to separate the two variables.
Using the strlen() function
The strlen() function is used to find the length of a string.
Let's find the length of our string "Hello world!":
<?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)
Using the strpos() function
The strpos() function is used to search for a string or character
within a string.
If a match is found in the string, this function will return the
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
|
As you see the position of the string "world" in our
string is position 6. The reason that it is 6, and not 7, is that the first
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
PHP String Functions
PHP String Introduction
The string functions allow you to manipulate strings.
Installation
The string functions are part of the PHP core. There is no
installation needed to use these functions.
PHP String Functions
PHP:
indicates the earliest version of PHP that supports the function.
Function
|
Description
|
PHP
|
Returns a string with backslashes in front of the specified
characters
|
4
|
|
Returns a string with backslashes in front of predefined
characters
|
3
|
|
Converts a string of ASCII characters to hexadecimal values
|
3
|
|
Alias of rtrim()
|
3
|
|
Returns a character from a specified ASCII value
|
3
|
|
Splits a string into a series of smaller parts
|
3
|
|
Converts a string from one Cyrillic character-set to another
|
3
|
|
Decodes a uuencoded string
|
5
|
|
Encodes a string using the uuencode algorithm
|
5
|
|
Returns how many times an ASCII character occurs within a string
and returns the information
|
4
|
|
Calculates a 32-bit CRC for a string
|
4
|
|
One-way string encryption (hashing)
|
3
|
|
Outputs strings
|
3
|
|
Breaks a string into an array
|
3
|
|
Writes a formatted string to a specified output stream
|
5
|
|
Returns the translation table used by htmlspecialchars() and
htmlentities()
|
4
|
|
Converts Hebrew text to visual text
|
3
|
|
Converts Hebrew text to visual text and new lines (\n) into
<br />
|
3
|
|
Converts HTML entities to characters
|
4
|
|
Converts characters to HTML entities
|
3
|
|
Converts some predefined HTML entities to characters
|
5
|
|
Converts some predefined characters to HTML entities
|
3
|
|
Returns a string from the elements of an array
|
3
|
|
Alias of implode()
|
3
|
|
Returns the Levenshtein distance between two strings
|
3
|
|
Returns locale numeric and monetary formatting information
|
4
|
|
Strips whitespace from the left side of a string
|
3
|
|
Calculates the MD5 hash of a string
|
3
|
|
Calculates the MD5 hash of a file
|
4
|
|
Calculates the metaphone key of a string
|
4
|
|
Returns a string formatted as a currency string
|
4
|
|
Returns specific local information
|
4
|
|
Inserts HTML line breaks in front of each newline in a string
|
3
|
|
Formats a number with grouped thousands
|
3
|
|
Returns the ASCII value of the first character of a string
|
3
|
|
Parses a query string into variables
|
3
|
|
Outputs a string
|
3
|
|
Outputs a formatted string
|
3
|
|
Decodes a quoted-printable string
|
3
|
|
Quotes meta characters
|
3
|
|
Strips whitespace from the right side of a string
|
3
|
|
Sets locale information
|
3
|
|
Calculates the SHA-1 hash of a string
|
4
|
|
Calculates the SHA-1 hash of a file
|
4
|
|
Calculates the similarity between two strings
|
3
|
|
Calculates the soundex key of a string
|
3
|
|
Writes a formatted string to a variable
|
3
|
|
Parses input from a string according to a format
|
4
|
|
Replaces some characters in a string (case-insensitive)
|
5
|
|
Pads a string to a new length
|
4
|
|
Repeats a string a specified number of times
|
4
|
|
Replaces some characters in a string (case-sensitive)
|
3
|
|
Performs the ROT13 encoding on a string
|
4
|
|
Randomly shuffles all characters in a string
|
4
|
|
Splits a string into an array
|
5
|
|
Count the number of words in a string
|
4
|
|
Compares two strings (case-insensitive)
|
3
|
|
Finds the first occurrence of a string inside another string
(alias of strstr())
|
3
|
|
Compares two strings (case-sensitive)
|
3
|
|
Locale based string comparison
|
4
|
|
Returns the number of characters found in a string before any
part of some specified characters are found
|
3
|
|
Strips HTML and PHP tags from a string
|
3
|
|
Unquotes a string quoted with addcslashes()
|
4
|
|
Unquotes a string quoted with addslashes()
|
3
|
|
Returns the position of the first occurrence of a string inside
another string (case-insensitive)
|
5
|
|
Finds the first occurrence of a string inside another string
(case-insensitive)
|
3
|
|
Returns the length of a string
|
3
|
|
Compares two strings using a "natural order" algorithm
(case-insensitive)
|
4
|
|
Compares two strings using a "natural order" algorithm
(case-sensitive)
|
4
|
|
String comparison of the first n characters (case-insensitive)
|
4
|
|
String comparison of the first n characters (case-sensitive)
|
4
|
|
Searches a string for any of a set of characters
|
5
|
|
Returns the position of the first occurrence of a string inside
another string (case-sensitive)
|
3
|
|
Finds the last occurrence of a string inside another string
|
3
|
|
Reverses a string
|
3
|
|
Finds the position of the last occurrence of a string inside
another string (case-insensitive)
|
5
|
|
Finds the position of the last occurrence of a string inside
another string (case-sensitive)
|
3
|
|
Returns the number of characters found in a string that contains
only characters from a specified charlist
|
3
|
|
Finds the first occurrence of a string inside another string
(case-sensitive)
|
3
|
|
Splits a string into smaller strings
|
3
|
|
Converts a string to lowercase letters
|
3
|
|
Converts a string to uppercase letters
|
3
|
|
Translates certain characters in a string
|
3
|
|
Returns a part of a string
|
3
|
|
Compares two strings from a specified start position (binary
safe and optionally case-sensitive)
|
5
|
|
Counts the number of times a substring occurs in a string
|
4
|
|
Replaces a part of a string with another string
|
4
|
|
Strips whitespace from both sides of a string
|
3
|
|
Converts the first character of a string to uppercase
|
3
|
|
Converts the first character of each word in a string to
uppercase
|
3
|
|
Writes a formatted string to a specified output stream
|
5
|
|
Outputs a formatted string
|
4
|
|
Writes a formatted string to a variable
|
4
|
|
Wraps a string to a given number of characters
|
4
|
PHP String Constants
PHP:
indicates the earliest version of PHP that supports the constant.
Constant
|
Description
|
PHP
|
CRYPT_SALT_LENGTH
|
Contains the length of the default encryption method for the
system. For standard DES encryption, the length is 2 |
|
CRYPT_STD_DES
|
Set to 1 if the standard DES-based encryption with a 2 character
salt is supported, 0 otherwise
|
|
CRYPT_EXT_DES
|
Set to 1 if the extended DES-based encryption with a 9 character
salt is supported, 0 otherwise
|
|
CRYPT_MD5
|
Set to 1 if the MD5 encryption with a 12 character salt starting
with $1$ is supported, 0 otherwise
|
|
CRYPT_BLOWFISH
|
Set to 1 if the Blowfish encryption with a 16 character salt
starting with $2$ or $2a$ is supported, 0 otherwise0
|
|
HTML_SPECIALCHARS
|
||
HTML_ENTITIES
|
||
ENT_COMPAT
|
||
ENT_QUOTES
|
||
ENT_NOQUOTES
|
||
CHAR_MAX
|
||
LC_CTYPE
|
||
LC_NUMERIC
|
||
LC_TIME
|
||
LC_COLLATE
|
||
LC_MONETARY
|
||
LC_ALL
|
||
LC_MESSAGES
|
||
STR_PAD_LEFT
|
||
STR_PAD_RIGHT
|
||
STR_PAD_BOTH
|
PHP Operators
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
|
PHP
If...Else Statements
The if, elseif and else 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.
- 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>
|
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 ($d=="Sun")
echo "Have a nice Sunday!";
else
echo "Have a nice day!";
?>
</body>
</html>
|
PHP Switch Statement
The Switch statement in PHP is used
to perform one of several different actions based on one of several different
conditions.
The Switch Statement
If you want to select one of many blocks of code to be executed,
use the Switch statement.
The switch statement is used to avoid long blocks of
if..elseif..else code.
Syntax
switch (expression)
{
case label1:
code to be executed if expression = label1;
break;
case label2:
code to be executed if expression = label2;
break;
default:
code to be executed
if expression is different
from both label1 and label2;
}
|
Example
This is how it works:
- A single expression (most often a variable) is evaluated once
- The value of the expression is compared with the values for each case in the structure
- If there is a match, the code associated with that case is executed
- After a code is executed, break is used to stop the code from running into the next case
- The default statement is used if none of the cases are true
<html>
<body>
<?php
switch ($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>
|
PHP Arrays
An array can store one or more
values in a single variable name.
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");
|
Example 2
In this example we assign the ID key manually:
$names[0] = "Peter";
$names[1] = "Quagmire";
$names[2] = "Joe";
|
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);
|
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?
|
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