LIS651 lecture 3
taming PHP
Thomas Krichel
2005-11-12
functions
• The PHP function reference is available on its
web site http://www.php.net/quickref.php. It shows
the impressive array of functions within PHP.
• But one of the strengths of PHP is that you can
create your own functions as you please.
• If you recreate one of the built-in functions, your
own function will have no effect.
example
• Stephanie Rubino was an English teacher and
objects to sentences like
You have ordered 1 bottles of Grosswald Pils.
• Let us define a function rubino_print(). It will take
three arguments
– a number to check for plural or singular
– a word for the singular
– a word for the plural
function and parameters
• use the keyword "function" and declare your
parameters, as in:
function rubino_print ($number, $singular,$plural) {
if($number == 1) {
print "one $singular";
}
else {
print "$number $plural";
}
}
default arguments
• Sometimes you want to allow a function to be
called without giving all its arguments. You can do
this by declaring a default value. For the previous
example
function thomas_need($thing='beer') {
print "I need $thing\n";
}
thomas_need();
// prints: I need beer
thomas_need('sex');
// prints: I need sex
rubino_print using common plurals
function rubino_print ($num, $sing,$plur=1) {
if($num == 1) {
print "one $sing";
}
elseif($plur ==1) {
print "$num $sing"."s";
}
else {
print "$num $plur";
}
}
return value
• Up until now we have just looked at the effect of a
function.
• return is a special command that return a value.
• When return is used, the function is left.
rubino_print with return
function rubino_print ($number, $singular,$plural) {
if($number == 1) {
return "one $singular";
}
return "$number $plural";
}
$order=rubino_print(2,"beer","beers");
print "you ordered $order\n";
// prints: you ordered 2 beers.
utility function from php.net
function mysql_fetch_all($query) {
$r=@mysql_query($query);
if($err=mysql_error()) { return $err;}
if(mysql_num_rows($r)) {
while($row=mysql_fetch_array($r)) {$result[]=$row; }
return $result;}}
if(is_array($rows=mysql_fetch_all($query)) {
// do something
}
else { if (! is_null($rows)) {
die("Query failed!");}
}
visibility of variables
• variables used inside a function are not visible
from the outside. Example
$beer="Karlsberg";
function yankeefy ($name='Sam Adams') {
$beer=$name;
}
yankeefy();
print $beer;
// prints: Karlsberg
• the variable inside the function is something
different than the variables outside.
accessing global variables.
• There are two ways to change a global variable,
i.e. one that is defined in the main script.
• One is just to call it as $GLOBAL['name'] where
name is the name of the global variable.
function yankeefy ($name="Sam Adams") {
$GLOBAL['beer']="name";
}
brewer_quiz.php: introduction
<?php
$brewers=array('Großwald Brauerei','Homburger Brauhaus',
'Karlsberg Brauerei','Ponter Hausbrauerei', 'Saarfürst
Merziger Brauhaus','Mettlacher Abtei-Bräu','Körpricher
Landbräu','Brauerei G.A. Bruch','Neufang Brauerei','Zum
Stiefel');
$form_top="<form action=\"$_SERVER[PHP_SELF]\"
method=\"get\"><p>\n";
$form_submit='<input type="submit" value="I try!"/>'."\n";
$form_end='<input type="hidden" name="submitted"
value="1"/></p></form>';
brewer_quiz.php: form building
function build_form($answer,$comment) {
print "<div>Take the Saarland brewery challenge</div>\n";
print $GLOBALS['form_top'];
print "<input type=\"text\" name=\"guess\"
value=\"$answer\"/>";
print $GLOBALS['form_submit']; print
$GLOBALS['submit_check'];
print $GLOBALS['form_end']; print $comment;
}
brewer_quiz.php: form processing
function process_form($answer,$brewers) {
$r[]=$answer;
foreach($brewers as $brew) {
if($answer == "$brew") {
$r[]='<div>Congradulation! This is correct!</div>';
return $r;
}
}
$r[]='<div>This is a bad answer, try again!</div>'; return $r;
}
brewer_quiz.php main part
if($_GET['submitted']) {
$from_form=process_form($_GET['guess'],$brewers);
}
build_form($from_form[0],$from_form[1]) ;
?>
working with many source files
• Many times it is useful to split a PHP script into
several files.
• PHP has two mechanisms.
• require(file) requires the to be included. If the file
is not there, PHP exits with an error.
• include(file) includes the file.
require() and include()
• Both assume that you leave PHP. Thus within
your included file you can write simple HTML.
• If you want to include PHP in your included file,
you have to surround it by <?php and ?>, just like
in a PHP script.
• Here is an example to use include to build the
basic web page.
top.html
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0
Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html>
<head><title>$title</title>
<meta http-equiv="content-type" content="text/html;
charset=UTF-8"/>
<link rel="stylesheet" type="text/css" href="main.css"/>
</head>
<body>
bottom.html
<p id="validator">
<a href="http://validator.w3.org/check?uri=referer"><img
style="border: 0pt"
src="http://wotan.liu.edu/valid-xhtml10.png"
alt="Valid XHTML 1.0!" height="31" width="88" /></a>
</p>
</body>
</html>
validated.php
<?php
$title="my basic page\n";
include("top.html");
print "<div>hello, world</div>";
include("bottom.html");
?>
trouble
• $title in the top.html is not understood as the title.
It reads as $title, which means "idiot" for your web
user.
• Even if you replace $title with
<?php $title ?>
$title is empty. The definition from the outer file is
not seen in the included file.
• So you have to split into three files, and print the
title in the main file. I leave that to you to figure
out.
login.php & create_account.php
• Both require a database that has three fields
– id which is an auto_increment int acting as a handle
– username is the username of the account. it must be
unique and this is enforced by mySQL
– password is a varchar(41) because the sha1 of the
password is stored. This is 40 chars long.
login.php
function show_form($message) {
print "<div><h1>$message</h1><h2>Login</h2>
<form action=\"$_SERVER[PHP_SELF]\" method=\"post\">
<div><input type=\"hidden\" name=\"submitted\" value=\"1\"
/></div><p>Username <input type=\"text\"
name=\"username\" maxlength=\"15\"
value=\"$_POST[username]\" /></p><p>Password <input
type=\"password\" name=\"pass\"
value=\"$_POST[pass]\"/></p><p><input type=\"submit\"
value=\"Login\" /> Not yet a member? <a
href=\"create_account.php\">Create an account</a>!
</p></form></div>";
}
function process_form() {
$username=trim($_POST['username']);
$pass=trim($_POST['pass']);
$sha_pass=sha1($pass);
$db=mysql_connect('localhost','krichel','laempel');
$query="SELECT * FROM beer_shop.users WHERE
username='$username' AND password = '$sha_pass'";
$result=mysql_query($query);
$error=mysql_error();
if($error) { return "Sorry: $query gives an error<br/>
$error"; }
$affected=mysql_affected_rows();
if(! ($affected)) {return "Invalid username or password";}
}
login.php (end)
if($_POST['submitted']) {
$error=process_form();
if($error) { show_form($error); }
else {
$user=$_POST['username'];
print "<h1>Welcome to $user</h1>";
}
}
else { show_form(''); }
create_account.php
function show_form($message) {
print "<div><h1>$message</h1><h2>Create
Account</h2><p>Please complete the form below to create
your account. </p> <form action=\"$_SERVER[PHP_SELF]
\" method=\"post\"><div><input type=\"hidden\"
name=\"submitted\" value=\"1\" /></div> It must be more
than 5 characters and cannot be your username.</p><p>
<input type=\"submit\" value=\"Create Account\" />
</p></form></div>";
create_account.php
<h3>Password</h3><p> Password <input type=\"password\"
name=\"pass1\" value=\"$_POST[pass1]\"/>Confirm
Password <input type=\"password\" name=\"pass2\"
value=\"$_POST[pass2]\"/> </p><p>The password you enter
will be used to access your account. It must be more than 5
characters and cannot be your username.</p> <p><input
type=\"submit\" value=\"Create Account\"
/></p></form></div>";
}
create_account.php
function process_form() {
$username=trim($_POST['username']);
$pass1=trim($_POST['pass1']);
$pass2=trim($_POST['pass2']);
if(strlen($username)<6) {
return "Username is too short.";
}
if(! ($pass1 == $pass2)) {return "Passwords do not match.";}
$pass=$pass1;
if($pass == $username) {
return "Your username can not be your password.";
create_account.php
if(strlen($pass)<6) {return "Password is too short.";}
$sha_pass=sha1($pass);
$db=mysql_connect('localhost','krichel','laempel');
$query="INSERT INTO beer_shop.users VALUES
('','$username','$sha_pass')";
$result=mysql_query($query);
$error=mysql_error();
1 for key 2") { return
if($error == "Duplicate entry '$username'
"Sorry: Username $username is already taken, choose
another.";
}
else {print "<h1>Thank you for registering with us!</h1>";}
}
create_account.php (end)
if($_POST['submitted']) {
$error=process_form();
if($error) {
show_form($error);
}
}
else {
show_form('');
}
sessions
• You will recall that HTTP is a stateless protocol.
Each request/response is self-contained.
• Statefulness is crucial in Web applications.
Otherwise users have to authenticate every time
they access a new page.
• Traditionally, one way to create statefullness is to
use cookies.
• PHP uses cookies to create a concept of its own,
sessions, that makes it all very easy.
cookies
• A cookie is a piece of attribute/value data. A
server can send cookies as value of a HTTP
header Set-Cookie:. Multiple headers may be
sent.
• When the client visits the web site again, it will
send the cookie back to the server with a HTTP
header Cookie:
Set-Cookie
• Set-Cookie: name=value; [expires= date;]
[path=path;] [domain= domain] [secure]
• where
–
–
–
–
name= is the variable name set in the cookie
value= is the variable's value
date= is a date when the cookie expires
path= restricts the cookie to be sent only when requests
to a path starting with path are made
– domain= restricts the sending of the cookie to a certain
domain
– secure restricts transmission to https
Cookies:
• The browser compares the request it wants to
make with the URL and the domain that sent the
cookie.
• If the path is not set the cookie will only be sent to
a request with the originating URL.
• If the cookie matches the request a request
header of the form
Cookie: name1=value1 ; name2=value2
is sent.
sessions
• Sessions are a feature of PHP. PHP remembers a
session through a special cookie PHPSESSID.
• To activate the sessions, include session_start();
at the beginning of your script, before any printing
has been done.
• One a session is active, you have a special
super-global variable $_SESSION. Session data
is stored in special files on wotan.
$_SESSION
• This is an array where you can read and set
variables that you want to keep during the
session.
if($_SESSION[user_name]) {
print "welcome $_SESSION[user_name]";
}
else {
// show users login form
print login_form();
}
ending sessions
• At 9 and 39 past each hour, wotan deletes all
session files that have not been changed for 24
minutes or more.
• If you want to remove a session yourself, you can
call session_destroy() in your script.
visit.php
<?php
$top='<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0
Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html><head><title></title><meta http-equiv="content-type"
content="text/html; charset=UTF-8"/>
</head><body><div>';
$bottom='</div><p>
<a href="http://validator.w3.org/check?uri=referer">
<img style="border: 0pt" src="/valid-xhtml10.png"
alt="Valid XHTML 1.0!" height="31" width="88" />
</a></p></body></html>';
visit.php
session_start();
$current=mktime(); // look at the current time
if($_SESSION[last_click]) {
$passed=$current-$_SESSION[last_click];
$to_print.="$passed seconds have passed since your last
visit.\n";
$_SESSION[last_click]=$current;
} else {
$to_print="This is your first visit.\n";
$_SESSION[last_click]=$current;
}
print "$top\n$to_print\n$bottom";
?>
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