CSCU9B3
An Introduction to PHP (1)
CSCU9B3
1
Web Processing in a Picture
Server Side
HTTP
Database for persistence Content
Client Side
Browser
Data
Scripting on the server
Content
Data
Scripting on the client
Access server scripts
from the client
Cookies
store
some
data
Not
Persistent
About the PHP Language
• PHP: Hypertext Preprocessor (earlier called
Personal Home Page)
– An HTML-embedded, server-side general
purpose scripting language for web development
• Syntax inspired by C
– Curly braces, semicolons
• Syntax inspired by perl
– Dollar signs to start variable names, associative
arrays
• Extends HTML to add segments of PHP
within an HTML file
CSCU9B3
3
PHP Introduction
• PHP is a scripting language
– PHP is interpreted by the server at run time,
so doesn’t need a compiler
• Doesn’t need a development environment
like Eclipse
• You can use a simple text editor like
TextPad
– Create files: e.g. mydemo.php
CSCU9B3
4
Running a PHP Program
• The PHP program is run on the server, so
no code is downloaded to the client
• Only the output from the PHP program is
sent to the client
• The easiest way to run a PHP program
and see its output is to put it on a (web)
server and open it in a browser
CSCU9B3
5
Getting Started
• On Windows, you can download and
install WAMP. With one installation and
you get an Apache webserver, MySQL
database server and PHP.
http://www.wampserver.com
• On Mac, you can download and install
MAMP.
http://www.mamp.info/en/index.html
CSCU9B3
6
Starting a PHP Program
<?php
?>
• Anything inside these delimiters is
interpreted as php
• Anything outside them is sent straight to
the client, usually the browser
– Typically HTML / CSS / Javascript code
CSCU9B3
7
Example 1
<HTML>
<head></head>
<body>
<H1>This is a PHP demo</H1>
<?php
print(“This is the output from the
PHP program”);
?>
</body>
</HTML>
http://wamp0.cs.stir.ac.uk/jli/example1.php
CSCU9B3
8
Example 2
<h1>Hello from Dr. Chuck's HTML Page</h1>
<p>
<?php
echo "Hi there.\n";
$answer = 6 * 7;
echo "The answer is $answer, what ";
echo "was the question again?\n";
?>
</p>
<p>Yes another paragraph.
</p>
PHP Program Structure
• In common with many programming
languages, PHP:
– Ends each line with a semi-colon ;
– Uses {} braces to delimit code blocks
• PHP can be used in either a procedural
or object-oriented way
• PHP denotes variables with the dollar
sign $a
CSCU9B3
Autumn 2019
10
Comments
• In PHP, we use // to
make a single-line
comment
• or /* and */ to make
a large comment
block
CSCU9B3
11
Naming convention of Variable
• A variable name must start with a letter or an
underscore ‘_’, not a number
• A variable name can only contain alpha-numeric
characters, underscores (a-z, A-Z, 0-9, and _ )
• A variable name should not contain spaces
– If it is more than one word, it should be separated with
an underscore ($my_string) or with capitalization
($myString)
CSCU9B3
12
Operators
• Operators are used to operate on values.
There are four classifications of operators
–
–
–
–
CSCU9B3
Arithmetic
Assignment
Comparison
Logical
13
Operators
CSCU9B3
14
Operators
CSCU9B3
15
Operators
CSCU9B3
16
Operators
CSCU9B3
17
Variables
• You assign variables like this:
$a=5;
• And compare them like this:
if($a==5)…
• You can use them in strings like this:
print(“$a is the value of variable a”);
CSCU9B3
18
Variable Types
• PHP is pretty relaxed about variable types
• You do not need to declare variables as being
of a certain type, just start using them:
<?php>
$a=5;
$a=“Hello”;
?>
• PHP automatically converts the variable to the
correct data type, depending on its value
CSCU9B3
19
Checking Variables
• You do not have to declare a variable before
you use it, but you should
• PHP will issue a warning (but still run) if you
access a variable that is undeclared:
$a=$b;
// $b never declared
• Use isset($var) to check if a variable has
been set
CSCU9B3
20
Conditional Statement: if
• To execute some code only if a specified
condition is true.
•
CSCU9B3
"Have a nice weekend!" if the current day is
Friday
21
Conditional Statement: if…else
• To execute some code if a condition is true and
another code if a condition is false.
CSCU9B3
22
Conditional Statement:
if...elseif...else
• 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!"
CSCU9B3
23
Conditional Statement: switch
• To select one of many blocks of code to be
executed
CSCU9B3
24
Arrays
• If you have a list of items (a list of car names,
for example), storing the cars in single
variables could look like this:
• However, what if you want to loop through the
cars and find a specific one? And what if you
had not 3 cars, but 300?
CSCU9B3
25
Arrays
• An array is a special variable, which can store
multiple values in one single variable
• An array can hold all your variable values
under a single name. You can access the
values by referring to the array name
• Each element in the array has its own index, so
that it can be easily accessed
CSCU9B3
26
Arrays
• In PHP, there are three kind of arrays:
•
Numeric array - An array with a numeric index.
Syntax: array(value1, value2, value3,...)
•
Associative array - An array where each ID key is
associated with a value
Syntax: array(key=>value, key=>value,
key=>value,...)
• Multidimensional array - An array containing one
or more arrays
CSCU9B3
27
Numeric Arrays
• Two methods to create a numeric array
• The index is automatically assigned (the index
starts at 0)
• The index is assigned manually:
Numeric Arrays
• Access the variable values by referring to the
array name and index
• The code above will output:
Associative Arrays
• With an associative array, each ID key is
associated with a value
• When storing data about specific named
values, a numerical array is not always the best
way to do it
• With associative arrays we can use the values
as keys and assign values to them
CSCU9B3
30
Associative Arrays
• In this example we use an array to assign ages
to the different persons:
• This example is the same as the one above,
but shows a different way of creating the array:
CSCU9B3
31
Associative Arrays
CSCU9B3
32
Multidimensional Arrays
• Sometimes you want to store values with
more than one key
• The dimension of an array indicates the
number of indices you need to select an
element
• In a multidimensional array, each element in
the main array can also be an array
• And each element in the sub-array can be an
array, and so on
CSCU9B3
33
Two-dimensional Arrays
• It is an array of arrays (a three-dimensional
array is an array of arrays of arrays).
$cars = array
(
array("Volvo",22,18),
array("BMW",15,13),
array("Saab",5,2),
array(“Audi",17,15)
);
CSCU9B3
Name
Stock
Sold
Volvo
22
18
BMW
15
13
Saab
5
2
Audi
17
15
34
Two-dimensional Arrays
<?php
echo $cars[0][0].": In stock:
sold: ".$cars[0][2].".<br>";
echo $cars[1][0].": In stock:
sold: ".$cars[1][2].".<br>";
echo $cars[2][0].": In stock:
sold: ".$cars[2][2].".<br>";
echo $cars[3][0].": In stock:
sold: ".$cars[3][2].".<br>";
?>
".$cars[0][1].",
".$cars[1][1].",
".$cars[2][1].",
".$cars[3][1].",
• The code will output
Volvo: In stock: 22, sold: 18.
BMW: In stock: 15, sold: 13.
Saab: In stock: 5, sold: 2.
Audi: In stock: 17, sold: 15.
Name
Stock
Sold
Volvo
22
18
BMW
15
13
Saab
5
2
Audi
17
15
Summary
• Basic concepts
• Operators
•
arithmetic, assignment, comparison, logical
• Variables
• Conditional statements
•
if, if…else, if…elseif…else, switch
• Array
•
CSCU9B3
numeric array, associative array, multidimensional
array
36
