Phpbasics

PHP Basics ● We will look at the language more formally later. ● For now –become familiar with the programming model –get familiar with server-side programming –get used to handling form submission PHP Basics 1

PHP: Hypertext Preprocessor Some References: www.php.net www.w3schools.com http://www.oreillynet.com/pub/ct/29 PHP Basics 2

A PHP Program ● contained in an HTML document. ● All code is found inside: <?php ... ?> tags. ● conditional HTML –you can have PHP control what HTML actually makes it to the output document. <?php if (foo) { ?> <h3> foo is true!</h3> <?php else ?> <h3> foo is false!</h3> PHP Basics 3

Web Server and PHP ● A client sends a request to a server, perhaps: GET /myprog.php HTTP/1.1 ● The server must be configured to recognize that the request should be handled by PHP. ● PHP reads the document myprog.php and produces some output (which is typically HTML). – all normal HTML tags are output without modification. PHP Basics 4

Our first PHP program? <html> <head> <title>I am a PHP program</title> </head> <body> <h3>PHP can handle HTML</h3> </body> </html> PHP Basics 5

A better example – try this <html> <head> <title>I am a PHP program</title> </head> <body> <?php phpinfo(); ?> </body> </html> PHP Basics

Server-side programming ● This is not like JavaScript – the browser does not understand PHP. ● You have to use a web server that supports php. – php preprocesses a file that contains HTML and code, and generates pure HTML (could actually be anything that the browser can understand). – If you “view source” in the browser, you can't tell the page was produced by php. PHP Basics 7

The Language in one slide ● Similar syntax to C/C++/Javascript – statements end with ';' – if, while, for, ... all just like we are used to. – assignment statements are the same. ● Variables are untyped (like Javascript) – can create a new variable by assigning a value. – variable names start with '$' ● arrays are different (associative arrays), but easy to get used to. PHP Basics 8

Generating HTML ● You can use functions echo , print and/or printf to generate HTML: <?php echo("<h3>Dynamic H3 tag</h3>"); print("<p>a paragraph produced with the print function</p>"); printf("<p>printf %s, works as well</p>n", "(from C)"); ?> PHP Basics 9

Jump right in! <h3>Here are some lines</h3> <?php variable names start with $ variables don't need to be declared. echo "<p>"; for ($i=0;$i<10;$i++) { echo "line " . $i . "<br>"; } echo "</p>"; string concatenation operator! ?> PHP Basics 10

First Exercise i 2i ---------------------------------- ● Create a PHP script that produces 1 2 an HTML table with the first 10 2 4 3 8 powers of two. 4 16 ● You need to use the pow() 5 32 6 64 function: 7 128 8 256 – pow(x,y) = xy 9 512 10 1024 PHP Basics 11

Non-obvious solution? <table border=1> <tr> <th>i</th> <th>2<sup>i</sup></th> </tr> <?php for ($i=1;$i<=10;$i++) { ?> <tr> <td> <?php echo($i); ?></td> <td> <?php echo pow(2,$i);?></td> </tr> <?php } ?> </table> PHP Basics 12

PHP style ● some PHP programmers think: – "I have an HTML document and I can add little bits of PHP code in special places" ● some others think: – "I have a PHP document in which I can add a few HTML tags". ● Use whatever style seems most comfortable to you. PHP Basics 13

PHP and forms ● Recall that an HTML form submission looks something like this (GET method): GET /somefile?x=32&name=Joe+Smith ● Typically a PHP script wants to get at the values the user typed into the form. – often the form itself came from a php script. PHP Basics 14

Form example <form method="GET" action="form.php"> <p> First Name: <input type="text" name="first"><br> Last Name: <input type="text" name="last"><br> <input type="submit"> </p> </form> PHP Basics 15

Receiving the submission ● You can put the form in a file named "form.php", and set the action to also be "form.php". – The php file will receive the submission itself – You could also leave off the action attribute ● Unless we add some php code, all that will happen when the form is submitted is that we get a new copy of the same form. PHP Basics 16

Form Fields and PHP ● PHP takes care of extracting the individual form field names and values from the query. – also does urldecoding for us. ● A global variable named $_REQUEST holds all the form field names and values. – this variable is an associative array – the keys (indicies) are the form field names. PHP Basics 17

Getting the values ● To get the value the user submitted for the field named "first": $_REQUEST['first'] ● To get the value the user submitted for the field named "last": $_REQUEST['last'] PHP Basics 18

Adding some PHP to the form ● We could simply print out the values entered (as HTML): <?php echo "<p>First name is "; echo $_REQUEST['first'] . "</p>"; echo "<p>Last name is "; echo $_REQUEST['last'] . "</p>"; ?> PHP Basics 19

Or do it like this <p>First name is <?php echo $_REQUEST['first'] ?> </p> <p>Last name is <?php echo $_REQUEST['last'] ?> </p> PHP Basics 20

Make a php form handler <form method="GET" action="form.php"> <p>First Name: <input type="text" name="first"><br> Last Name: <input type="text" name="last"><br> <input type=submit> </p></form> <?php echo "<p>First name is "; echo $_REQUEST['first'] . "</p>"; echo "<p>Last name is "; echo $_REQUEST['last'] . "</p>"; ?> PHP Basics 21

Looking for Joe Smith ● We can easily turn this into a primitive login system. – we only allow Joe Smith to login – If the name is not Joe Smith, we send back the form along with a rude message. ● A real login system would not have the valid login names (passwords) hard-coded in the program – probably coming from a database. PHP Basics 22

Login handling form <?php if (($_REQUEST['first'] == "joe") && ($_REQUEST['last'] == "smith")) { echo "<p>Welcome back joe</p>; } else { ?> <p>You are not the correct person.</p> <p>Try again</p> <form method="GET" action="form.php"> <p>First Name: <input type="text" name="first"><br> Last Name: <input type="text" name="last"><br> <input type=submit> </p></form> PHP Basics 23 <?php } ?>

Exercise ● Create a php script with a form where the user enters a number between 1 and 10. ● If they guess correctly, tell them! ● If they guess wrong – send the form back. ● Play with your php program directly (skipping the form) by constructing URLs manually. PHP Basics 24

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