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Introduction to PHP: Basics, Syntax, and Database Access

PHP is a powerful server-side scripting language widely used for web development. It can be embedded into HTML and is easy to learn, especially for those familiar with C. This guide covers the basics of PHP, including variables, arrays, database connectivity, and form handling using GET and POST methods. You will also learn how to set up a PHP environment with Apache and MySQL, and how to execute PHP scripts from a web server. Get started with dynamic web applications and hone your PHP skills today!

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Introduction to PHP: Basics, Syntax, and Database Access

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  1. Basic php

  2. Php • Official site: www.php.net • PhP manual: http://www.php.net/manual/en/index.php • Useful package (Apache, MySql,PhP): http://www.easyphp.org/

  3. Where ? • Ssh into cobweb.seas.gwu.edu and put your php files. Make sure they are readable by everyone. • Access them via http://www.student.seas.gwu.edu/~yourusername/filename.php

  4. What is PhP • “PHP is a widely-used general-purpose scripting language that is especially suited for Web development and can be embedded into HTML” (www.php.net) • Server scripting language (Javascript is a client side scripting language) • If you know C, you will learn PhP in no time.

  5. Hello World! • Index.php: <html> <head>  <title>PHP Test</title> </head> <body> <?php echo '<p>Hello World</p>'; ?></body></html> • Output <html>: <head> <title>PHP Test</title> </head> <body> <p>Hello World</p> </body> </html>

  6. Basics • Use echo for printing • Variables start with $ sign • Do not have to explicitly assign them a type (like int, array, etc.) • If $x=3 and $a=’x’, echo $$a will display 3, because $$a=$($a)=$x=3; • . (dot) concatenates 2 strings. Ex $a=”Hello”;$b=”World”; echo $a.” ”.$b; displays ”Hello World”

  7. Accesing databases from PhP <html>  <head>   <title>PHP Test</title>  </head>  <body> <?php $link=mysql_connect("localhost",“username",“password") or die("Error connecting to the database server:".mysql_error()."<br>\n"); mysql_select_db(“username") or die("Error selecting the database:".mysql_error()."<br>\n"); ?> <?php $sql = "SELECT fname, sid FROM students;"; $result=mysql_query($sql); while(list($name,$id) = mysql_fetch_array($result)) { echo "<p>".$name." ".$id; } ?> </body> </html>

  8. Arrays • A mapping between keys and values. Example <?php$arr = array("foo" => "bar", 12 => true);echo $arr["foo"]; // barecho $arr[12];    // 1 foreach ($arr as $key => $value) { echo “key=”.$key; echo “ value=”,$value.”<BR>”; } ?>

  9. Get and Post • $_GET[’variablename’] – the variable is appended to the http address, and is transmited in the same stream. Ex: http://www.somesite.com/index.php?a=1&b=’x’. Easy to bookmark • $_POST[’variablename’] – a new stream is created, and all the post variables are transmited in this stresm. The http address is clean (no bookmarks)

  10. Get variables from forms Action.php <HTML> <BODY> <?php echo "Your name is ".$_POST["name"]." and you are ".$_POST["age"]." years old";?> </BODY> </HTML> getName.html <HTML> <BODY> <form action="action.php" method="post"> <p>Your name: <input type="text" name="name" /></p> <p>Your age: <input type="text" name="age" /></p> <p><input type="submit" value="Submit"/></p> </form> </BODY> </HTML> Exercise: try it with “get” now.

  11. Some usefull global variables • $_SERVER[’PHP_SELF’]- The filename of the currently executing script, relative to the document root. For instance, $_SERVER['PHP_SELF'] in a script at the address http://example.com/test.php/foo.bar would be /test.php/foo.bar. • $_SERVER['SERVER_NAME']- The name of the server host under which the current script is executing. If the script is running on a virtual host, this will be the value defined for that virtual host. • $_SESSION -An associative array containing session variables available to the current script. • __LINE__The current line number of the file. • __FILE__The full path and filename of the file. If used inside an include, the name of the included file is returned.

  12. Session • HTTP is stateless • Simulates a statefull connection. Maintains records on the server side until the browser is closed. • session_start(); • $_SESSION[‘foo’]=‘bar’; • $_SESSION[‘a’][‘b’]=‘c’; • Allows to build a ”shoping cart”;

  13. Includes • header.php • <html> •  <head> •   <title>PHP Test</title> •  </head> •  <body> • <TABLE width="800" cellpadding="4" cellspacing="0" align="center" border="0"> • <TR> • <TD width='100%'> • footer.php • </TD> • </TR> • </TABLE> • </body> • </html> • index.php • <?php • include ”header.php”; • echo ”hello world”; • include ”footer.php” • ?>

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