What is PHP?
PHP (recursive acronym for "PHP: Hypertext Preprocessor") is a widely-used Open Source general-purpose scripting language that is especially suited for Web development and can be embedded into HTML.
• 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
PHP Syntax
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 . A PHP scripting block can be placed anywhere in the document.
On servers with shorthand support enabled you can start a scripting block with .
For maximum compatibility, we recommend that you use the standard 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:
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.
Something Useful
Let us do something more useful now. We are going to check what sort of browser the visitor is using. For that, we check the user agent string the browser sends as part of the HTTP request. This information is stored in a variable. Variables always start with a dollar-sign in PHP. The variable we are interested in right now is $_SERVER['HTTP_USER_AGENT'].
Note:
$_SERVER is a special reserved PHP variable that contains all web server information. It is known as a superglobal
To display this variable, you can simply do:
A sample output of this script may be:
Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1)
PHP Variables
A variable is used to store information.
Variables in PHP
Variables are used for storing a 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 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)
• String Variables in PHP
• String variables are used for values that contains 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:
• The output of the code above will be:
Hello World
• 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 Forms and User Input
The PHP $_GET and $_POST variables are used to retrieve information from forms, like user input.
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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:
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:
Welcome !
You are years old.
Output could be something like this:
Welcome John!
You are 28 years old.
PHP $_GET Function
The built-in $_GET function is used to collect values in a form with method="get".
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The $_GET Function
The built-in $_GET function is used to collect values from a form sent 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 (max. 100 characters).
Example
When the user clicks the "Submit" button, the URL sent to the server could look something like this:
http://www.example.com/welcome.php?fname=Peter&age=37
The "welcome.php" file can now use the $_GET function to collect form data (the names of the form fields will automatically be the keys in the $_GET array):
Welcome .
You are years old!
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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 large variable values; the value cannot exceed 100 characters.
PHP $_POST Function
The built-in $_POST function is used to collect values in a form with method="post".
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The $_POST Function
The built-in $_POST function 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
When the user clicks the "Submit" button, the URL will look like this:
http://www.example.com/welcome.php
The "welcome.php" file can now use the $_POST function to collect form data (the names of the form fields will automatically be the keys in the $_POST array):
Welcome !
You are years old.
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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.
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File Upload:
$_FILES['userfile']['name']
The original name of the file on the client machine.
$_FILES['userfile']['type']
The mime type of the file, if the browser provided this information. An example would be "image/gif". This mime type is however not checked on the PHP side and therefore don't take its value for granted.
$_FILES['userfile']['size']
The size, in bytes, of the uploaded file.
$_FILES['userfile']['tmp_name']
The temporary filename of the file in which the uploaded file was stored on the server.
$_FILES['userfile']['error']
The error code associated with this file upload. This element was added in PHP 4.2.0
Code:
$file = $_FILES['userfile']['name'];
$path = “image/”.$file;
if (move_uploaded_file($_FILES['userfile']['tmp_name'], $path)) {
echo "File is valid, and was successfully uploaded.\n";
} else {
echo "Possible file upload attack!\n";
}
echo 'Here is some more debugging info:';
print_r($_FILES);
?>
Upload Multiple files:
Code:
$error) {
if ($error == UPLOAD_ERR_OK) {
$tmp_name = $_FILES["pictures"]["tmp_name"][$key];
$name = $_FILES["pictures"]["name"][$key];
move_uploaded_file($tmp_name, "data/$name");
}
}
?>
