php
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IS2803
Developing Multimedia
Applications for Business (Part 2)
Lecture 3: Working with PHP
Rob Gleasure
R.Gleasure@ucc.ie
www.robgleasure.com
IS2803
Today’s lecture
PHP variable types
Conditional statements
Loops
Functions
Comments
PHP variable types
As mentioned last week, PHP scripts are embedded within HTML
between a <?php opening tag and ?> closing tag
E.g., here is simple 'Hello World' page
<html>
<head><title>Hello PHP</title>
</head>
<body>
<?php
echo "Hello World!";
?>
</body>
</html>
PHP variable types
We also spoke about variable scope
<html>
<head><title>String Concatenation</title>
</head>
<body>
<?php
$x = 0;
// this variable is created outside any functions, i.e. is 'global'
function functionName () {
$x = 1;
/* this makes a new $x, as the $x already
created is out of scope */
}
functionName();
echo "X is ".$x;
// this will print out 0
?>
</body>
</html>
PHP variable types
The global keyword lets a function know a variable exists globally
<html>
<head><title>String Concatenation</title>
</head>
<body>
<?php
$x = 0;
// this variable is created outside any functions, i.e. is 'global'
function functionName(){
global $x;
/* now $x is the same as outside the function*/
$x = 1;
}
functionName();
echo "X is ".$x; // this will now print out 2
?>
</body>
</html>
PHP variable types
Variables created within a function are destroyed when that function
ends
<html>
<head><title>String Concatenation</title>
</head>
<body>
<?php
$x = 0;
// this variable is created outside any functions, i.e. is 'global'
function functionName(){
global $x;
/* now $x is the same as outside the function*/
$x = 1;
$y = 2;
}
functionName();
echo "X is ".$x; // this will print out 2
echo "<br>";
echo "Y is ".$y; // this will create a new null reference $y and print that
?>
</body>
</html>
PHP variable types
The static keyword stops variables being destroyed
<html>
<head><title>String Concatenation</title>
</head>
<body>
<?php
$x = 0;
// this variable is created outside any functions, i.e. is 'global'
function functionName(){
global $x;
/* now $x is the same as outside the function*/
$x = 1;
static $y;
$y = $y+2;
}
functionName();
echo "X is ".$x; // this will print out 2
echo "<br>";
echo "Y is ".$y; // this still won't work, as $y can still only be accessed in functionName()
?>
</body>
</html>
PHP variable types
When we want to export these static variables, our best way is by
returning them
<html>
<head><title>String Concatenation</title>
</head>
<body>
<?php
$x = 0;
// this variable is created outside any functions, i.e. is 'global'
function functionName(){
global $x;
/* now $x is the same as outside the function*/
$x = 1;
static $y;
$y = $y+2;
return $y;
}
echo "Y is ".functionName();
// this will print out 2
echo "<br>";
echo "X is ".$x; echo "<br>";
// this will print out 2
echo "Y is ".functionName();
// now this will print out 4
?>
</body>
</html>
PHP variable types
PHP variables are Loosely Typed
this means you do not need to declare a variable type. To store
a value as a string, it is simply provided in, whilst numbers are
provided without quotes
e.g.
<?php
$txt = 'Hello';
$x = 16;
?>
//this is stored as a string
//this is stored as an integer
PHP strings
The most common form of manipulation is concatenation, where
multiple strings are combined into one. This is done in PHP simply
by putting a full-stop between each string segment, e.g.
<html>
<head><title>String Concatenation</title>
</head>
<body>
<?php
$txt1 = 'Another beautiful day… ';
$txt2 = 'Writing code.';
$txt3 = $txt1.$txt2;
echo $txt3;
?>
</body>
</html>
PHP strings
There are also numerous other functions, which search for the
existence of substrings, check the length of a string, replace parts of
strings, etc.
A complete set of string-related functions can be found at
http://www.w3schools.com/php/php_ref_string.asp
PHP numeric variables
Numeric variables in PHP have basically 3 kinds of operators
Arithmetic operators
Commonly we use: +, -, *, /, %, ++, and –
Assignment operators
Commonly we use: =, +=, and -=
Comparison operators
Commonly we use: ==, !=, >, <, >=, and <=
PHP arrays
In addition to numeric and string variables, PHP also allows for
arrays
As we saw already in JavaScript, arrays are basically a way to store
a collection of related variables
Each value stored in an array is contained at a specific index,
beginning with the index 0
You can find a complete reference of array-related PHP functions at
http://www.w3schools.com/php/php_ref_array.asp
PHP arrays
There are two ways to declare an array, e.g. if we wanted to make
an array called $names to store the three string values ‘Enda’,
‘Eamon’, and ‘Micheal’, we would write it in one line
$names=array('Enda','Eamon','Micheal');
Or we could assign the index manually
$names[0] = 'Enda';
$names[1] = 'Eamon';
$names[2] = 'Micheal';
If we later wanted to print out the value of the first value in $names,
we could write
echo $names[0] ;
// this will print out 'Enda'
PHP arrays
Try out the following code
<html>
<head><title>Arrays</title>
</head>
<body>
<?php
$namesA = array('Stan','Kyle');
$namesB[0] = 'Brian';
$namesB[1] = 'Meg';
echo $namesA[1];
echo "<br>";
echo $namesB[1];
?>
</body>
</html>
PHP arrays
Note: if you don’t want a strictly ordered array, you can also use
values as array keys in what are termed associative arrays
e.g.
<html>
<head><title>Arrays</title>
</head>
<body>
<?php
$food_order["Max"] = 'Pizza';
$food_order["Jane"] = 'Salad';
$food_order["Alex"] = 'Crab';
echo "Max wants: ".$food_order["Max"]."<br />";
echo "Jane wants: ".$food_order["Jane"]."<br />";
echo "Alex wants: ".$food_order["Alex"];
?>
</body>
</html>
Conditional statements in PHP
The same logical operators exist for both string and numeric
variables in PHP as JavaScript, facilitating the same conditional
statements
Commonly we use: &&, ||, and !, in combination with comparison
operators for numeric variables, or comparison functions for string
variables
In this way, we can check to see if certain conditions are met before
deciding whether to execute some piece of code or loop
If-Else Loops in PHP
Our if-else statements look much the same,
e.g.
if ($var == 0 && strlen($var2) > 1) {
//do something
elseif ($var == 5 && strlen($var2) > 10) {
//do something else
}else{
//do default thing
}
Remember, only one piece of code will be executed, then the rest of
the if-else statements will be skipped. This means if numerous if
conditions are true, only the code in the first if loop will be executed.
If-Else Loops in PHP
Try out the following code
<html>
<head><title>Arrays</title>
</head>
<body>
<?php
$cat_has_funny_face = 'true';
if ($cat_has_funny_face == 'true'){
echo "This cat can have cheeseburgers. ";
}else{
echo "This cat may not have cheeseburgers, that's ridiculous. ";
}
?>
</body>
</html>
While loops in PHP
Our while loops are also much the same in PHP
e.g.
while ($my_var == ‘false’) {
/*
This piece of code will keep executing until something
changes the value of $my_var to be something other than
‘false’
*/
}
As are for-loops
e.g.
for ($num = 0; $num < 10; $num ++){
//do this code;
}
Functions in PHP
Functions also work in much the same way as JavaScript
New functions are created using the function keyword, followed
by the name and parentheses describing any arguments
The block of code contained within a function is surrounded by
curly brackets, i.e. { …. }
Every function returns a value in one of two ways
1)
By using the keyword return
2)
If no return statement is present, then a default value of null
is returned
PHP function names must begin with a letter or underscore
(although unlike PHP variables, function names don’t begin with a
dollar sign)
Functions in PHP
Once we have created a function, we can then reference it
elsewhere
e.g.
Note that arguments’
<html>
<head><title>PHP Functions</title>
</head>
<body>
<?php
function squareValue ($value) {
return $value*$value;
}
echo squareValue(4);
?>
</body>
</html>
names in PHP are
also preceded by $
Comments in PHP
We also still use // to make a single-line comment or /* and */ to
make a large comment block.
e.g.
<html>
<body>
<?php
// This is a comment on one line
/*
This is a block of commented text,
which can continue over several lines
*/
?>
</body>
</html>
HTML forms and PHP
When we discussed HTML inputs in lecture 20, we didn't really
discuss the fact they are often wrapped in a <form> tag
e.g.
<form>
First name: <input type="text" name="firstname"><br>
Last name: <input type="text" name="lastname">
<input type="submit" value="submit details">
</form>
However the <form> tag and its functionality becomes much more
useful once we start using PHP
A common use of PHP is to have HTML forms gather information,
then send it to a PHP script on the server for processing
HTML forms and PHP
Forms come with two special attributes surrounding this ability to
gather information and send it to a script
The action attribute specifies the URL to send the data
The method attribute specifies how to send this data
e.g.
<form action="myScript.php" method="post">
First name: <input type="text" name="firstname"><br>
Last name: <input type="text" name="lastname">
<input type="submit" value="submit details">
</form>
HTML forms and PHP
Save the following code as lecture3.php
<html>
<head>
<script type="text/javascript">
function formSubmit() {
document.getElementById("myForm").submit();}
</script>
</head>
<body>
<p>Enter your details and press the "Submit form" button to submit the form.</p>
<form id="myForm" action="form1.php" method="get">
First name: <input type="text" name="firstName" /><br />
Last name: <input type="text" name="lastName" /><br />
Home address: <input type="text" name="homeAddress" /><br />
Email address: <input type="text" name="emailAddress" /><br />
<input type="button" onclick="formSubmit()" value="Submit form" />
</form>
</body>
</html>
HTML forms and PHP
Save the following code as form1.php
<html>
<body>
<?php
$fname = $_GET["firstName"];
$lname = $_GET["lastName"];
$home = $_GET["homeAddress"];
$email = $_GET["emailAddress"];
$subject = "Hi!";
$body = "Your name is ".$fname." ".$lname.".<br> Your email is ".$email.", and
you live at ".$home;
echo $body."<br><br>";
echo "Incidentally, check out the URL in the header.";
?>
</body>
</html>
HTML forms and PHP
So how did form1.php handle the data that we sent it?
Method = 'get'
The predefined $_GET variable is used to collect values from a form
sent with method='get'
$_GET is essentially an associative array, so you need to specify
which input field you wish to obtain data from
$fname = $_GET["firstName"];
Note that this means it is crucial that the page containing the form
provides input fields with a name attribute
Method = 'post'
We could also have sent the data from the form with method = 'post',
in which case we would use the predefined $_POST variable
<form id="myForm" action= “form1.php" method="post">
Like $_GET, $_POST is essentially an associative array, so you
need to specify which input field you wish to obtain data from
$fname = $_POST["firstName"];
Again, it is crucial that the page containing the form provides input
fields with a name attribute
Get vs. Post
The difference is that 'get' sends the data in the URL header,
whereas 'post' hides the data is the http request
This means 'get' requests are less private but more efficient and
easy to bookmark and/or re-execute
However 'post' data is better when information is private or when
large quantities are being provided
HTML forms and PHP
Try out the following code in lecture3.php
<html>
<head>
<script type="text/javascript">
function formSubmit() {
document.getElementById("myForm").submit();}
</script>
</head>
<body>
<p>Enter your details and press the "Submit form" button to submit the form.</p>
<form id="myForm" action="form1.php" method="post">
First name: <input type="text" name="firstName" /><br />
Last name: <input type="text" name="lastName" /><br />
Home address: <input type="text" name="homeAddress" /><br />
Email address: <input type="text" name="emailAddress" /><br />
<input type="button" onclick="formSubmit()" value="Submit form" />
</form>
</body>
</html>
HTML forms and PHP
Then save this in form1.php
<html>
<body>
<?php
$fname = $_POST["firstName"];
$lname = $_POST["lastName"];
$home = $_POST["homeAddress"];
$email = $_POST["emailAddress"];
$subject = "Hi!";
$body = "Your name is ".$fname." ".$lname.".<br> Your email is ".$email.", and
you live at ".$home;
echo $body."<br><br>";
echo "Look at the difference in the URL.";
?>
</body>
</html>
PHP and Cookies
As we saw earlier in the year, a cookie is a small file that the server
embeds on the user's computer. Each time the same computer
requests a page with a browser, it will send the cookie too.
The setcookie() function is used to set a cookie. It commonly takes
three arguments
The name of the cookie
The value of the cookie
The expiration date of the cookie (in seconds). Note that if no
time is set (or '0'), the cookie will expire when the browser closes
e.g.
setcookie ('car', 'toyota', '3600') //expires in an hour
PHP and Cookies
Similar to our $_GET and $_POST variables, cookies can be
retrieved using a special associative array, i.e. $_COOKIE[]
$my_var = $_COOKIE['car']
// $my_var will contain the string 'toyota'
We can check if a cookie is set by using the isset function
if(isset($_COOKIE['car'])) {
echo $_ COOKIE['car'] }
We delete cookies simply by setting the expiration date to be in the
past
setcookie ('car", '"", '-3600')
PHP and Cookies
Try out the following code
<html>
<head>
<script type="text/javascript">
function formSubmit() {
document.getElementById("myForm").submit();}
</script>
</head>
<body>
<?php
if (isset($_COOKIE["username"])){
echo "Hi there ".$_COOKIE["username"];
}
?>
<p>Enter your details and press the "Submit form" button to submit the form.</p>
<form id="myForm" action="http://corvus2.ucc.ie/phd/rgleasure/is4428/php_files/cookie2.php" method="post">
First name: <input type="text" name="firstName" /><br />
Last name: <input type="text" name="lastName" /><br />
<input type="button" onclick="formSubmit()" value="Submit form" />
</form>
</body>
</html>
PHP and Cookies
Then copy this into form1.php
<html>
<body>
<?php
$fname = $_POST["firstName"];
$lname = $_POST["lastName"];
// create a cookie called 'username' to store the combined first and last name sent
setcookie ('username', $fname." ".$lname);
// redirect back to cookie1.php
header( 'Location: http://corvus2.ucc.ie/phd/rgleasure/is4428/php_files/cookie1.php' ) ;
?>
</body>
</html>
PHP and Session Variables
Session variables are almost identical to cookies, except they store
the information on the server, rather than the browser
Session variables hold information on the server about one single
user, and are available to all pages in one application
Sessions work by creating a unique id (UID) for each visitor and
store variables based on this UID. The UID is either stored in a
cookie or is propagated in the URL (don't worry about this for now).
PHP and Session Variables
The first thing we must do is start up the session
<?php
session_start();
?>
We may then store and retrieve session variables using another
dedicated associative array, i.e. $_SESSION[]
$_SESSION['my_session_var'] = 'Hello World!';
echo $_SESSION['my_session_var'];
PHP and Session Variables
To check whether a session variable is set, we can use the isset()
function
if(isset($_SESSION['my_session_var'])) {
echo $_SESSION['my_session_var'];}
When we wish to remove the session variables for a user, we can
either remove a specific session variables with unset()
unset($_SESSION['my_session_var']);
Or all session variables for that user
session_destroy();
HTML forms and PHP
Try out this code in lecture3.php
<html>
<head>
<script type="text/javascript">
function formSubmit() {
document.getElementById("myForm").submit();}
</script>
</head>
<body>
<?php
session_start();
if (isset($_SESSION["username"])){
echo "Hi there ".$_SESSION["username"];
}
?>
<p>Enter your details and press the "Submit form" button to submit the form.</p>
<form id="myForm" action= "form1.php" method="post">
First name: <input type="text" name="firstName" /><br />
Last name: <input type="text" name="lastName" /><br />
<input type="button" onclick="formSubmit()" value="Submit form" />
</form>
</body>
</html>
HTML forms and PHP
And this code in form1.php
<html>
<body>
<?php
$fname = $_POST["firstName"];
$lname = $_POST["lastName"];
//start the session
session_start();
// create a session variable called 'username' to store name
$_SESSION['username'] = $fname." ".$lname;
// redirect back to cookie1.php
header( 'Location: lecture3.php' ) ;
?>
</body>
</html>
Exercise
Add the following text to a new page in your folder in htdocs and
save it as lecture3a.php
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<META http-equiv="Content-Type" content="text/html; charset=ISO-8859-5">
<title>Lecture 3 main page</title>
</head>
<body>
<h2> Welcome to lecture 3</h2>
<form>
Enter Login name <input type="text" >
Enter password <input type="password" >
<input type="submit" value ="login">
</form>
</body>
</html>
Exercise
Now add the following text to another new page in your folder in
htdocs and save it as lecture3b.php
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<META http-equiv="Content-Type" content="text/html; charset=ISO-8859-5">
<title>Lecture 3 login handler</title>
</head>
<body>
<?php
// create a variable called $username and set it to store the value posted as 'login_name'
//start the session
// create a session variable called 'username' to store the user's name
// redirect back to cookie1.php
?>
</body>
</html>
Exercise
Add ‘send’ functionality to the form in lecture3a.php. This will require
Set the name attribute of the login textfield to 'login_name'
Set the name attribute of the password textfield to 'pword'
Adding an action attribute to the form which specifies the relative
URL of lecture3b.php
Specifying a communication method (go for post)
Exercise
Next add the missing lines in lecture3b.php, i.e.
Create a variable called $username and set it to store the value
posted as 'login_name'
Start the session
Create a session variable called 'username' to store the user's
name
Redirect back to lecture3a.php
Exercise
Lastly, see if you can figure out how you can add PHP to
lecture3a.php such that the form only displays when a user has not
already entered a name and password and submitted that
information. If the user has already entered a name, it should
instead display "Hello " and the person's name, e.g. "Hello Tod"
This requires that you:
Start the session
Check if $_SESSION[‘username'] is set
If yes, display Hello " and the person's name
If no, then use the echo command to output each whole line of
HTML as a string
Want to read more?
Links and references
Some PHP tutorials
http://www.php.net/
http://www.tizag.com/phpT/
http://www.w3schools.com/php
