Web development

What is PHP? PHP stands for P HP: H ypertext P reprocessor 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 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

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. <?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.

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>

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; Let's try creating a variable containing a string, and a variable containing a number: <?php $txt="Hello World!"; $x=16; ?>

Variable 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, 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) In PHP, a variable does not need to be declared before adding a value to it. the variable is declared automatically when you use it. 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.

The if...elseif....else Statement 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>

The PHP Switch Statement 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. <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>

The while Loop 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>

The do...while Statement 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>

The for Loop 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>

The foreach Loop 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. 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>

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. 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>

PHP Form Handling When a user fills out the form in the previous slide 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>

HTML Form GET Method 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. $_GET is used to receive the form values in the PHP pages.

HTML Form POST Method 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. $_POST is used to receive the form values in the PHP page.

PHP $_REQUEST The PHP built-in $_REQUEST function contains the contents of both $_GET, $_POST, and $_COOKIE. The $_REQUEST function can be used to collect form data sent with both the GET and POST methods. Welcome <?php echo $_REQUEST["fname"]; ?>!<br /> You are <?php echo $_REQUEST["age"]; ?> years old.

Server Side Includes You can insert the content of one PHP file into another PHP file before the server executes it, with the include() or require() function. The two functions are identical in every way, except how they handle errors: include() generates a warning, but the script will continue execution require() generates a fatal error, and the script will stop These two functions are used to create functions, headers, footers, or elements that will be reused on multiple pages. Server side includes saves a lot of work. This means that you can create a standard header, footer, or menu file for all your web pages. When the header needs to be updated, you can only update the include file, or when you add a new page to your site, you can simply change the menu file (instead of updating the links on all your web pages).

PHP include() Function The include() function takes all the content in a specified file and includes it in the current file. If an error occurs, the include() function generates a warning, but the script will continue execution. Assume that you have a standard header file, called "header.php". To include the header file in a page, use the include() function: <html> <body> <?php include("header.php"); ?> <h1>Welcome to my home page!</h1> <p>Some text.</p> </body> </html>

PHP require() Function The require() function is identical to include(), except that it handles errors differently. If an error occurs, the include() function generates a warning, but the script will continue execution. The require() generates a fatal error, and the script will stop. <html> <body> <?php require("wrongFile.php"); echo "Hello World!"; ?> </body> </html> Error message: Warning: require(wrongFile.php) [function.require]: failed to open stream: No such file or directory in C:omeebsiteest.php on line 5 Fatal error: require() [function.require]: Failed opening required 'wrongFile.php' (include_path='.;C:hp5ear') in C:omeebsiteest.php on line 5

PHP Exception Handling <?php //create function with an exception function checkNum($number) { if($number>1) { throw new Exception("Value must be 1 or below"); } return true; } //trigger exception in a "try" block try { checkNum(2); //If the exception is thrown, this text will not be shown echo 'If you see this, the number is 1 or below'; } //catch exception catch(Exception $e) { echo 'Message: ' .$e->getMessage(); } ?>

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