week 4- intro to php
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Important!
Please use the following site to test yourPhp codes (as of this moment).
http://codepad.org/
->and select Php -> write the codes on the text area
provided , the click submit
http://codepad.org/http://codepad.org/ -
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Learning PHP
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Drawbacks of HTML
HTML only allows for creating static webpages, or web pages that do not change
It does not, by itself, provide a way for
users to interact
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Learning PHP
PHP is a powerful server-side scripting languagefor creating dynamic and interactive websites.
PHP is the widely-used and free.
PHP is perfectly suited for Web developmentand can be embedded directly into the HTMLcode.
The PHP syntax is very similar to C.
PHP is often used together with Apache (webserver) on various operating systems.
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Introduction to PHP
A PHP file may contain text, HTML tagsand scripts.
Scripts in a PHP file are executed on the
server.
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How PHP Works
When a user navigates in her browser to a page that ends with a .php extension, the request is sent to a webserver, which directs the request to the PHP interpreter.
As shown in the diagram above, the PHP interpreter processes the page, communicating with file systems,databases, and email servers as necessary, and then delivers a web page to the web server to return to thebrowser.
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What You Should Already Know
Before you continue you should have abasic understanding of the following:
HTML / XHTML
Some scripting knowledge
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What is PHP?
PHP standsfor PHP: Hypertext Preprocessor
PHP is a server-side scripting language
PHP scripts are executed on the server PHP supports many databases (MySQL,
etc.)
PHP is an open source software PHP is free to download and use
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What is a PHP File?
PHP files may contain text, HTML tagsand scripts
PHP files are returned to the browser as
plain HTML PHP files have a file extension of ".php",
".php3", or ".phtml"
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Why PHP?
PHP runs on different platforms (Windows,Linux, Unix, etc.)
PHP is compatible with almost all servers
used today (Apache, etc.) PHP is FREE to download from the official
PHP resource:www.php.net
PHP is easy to learn and runs efficientlyon the server side
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Where to Start?
Install an Apacheserver on a Windows orLinux machine
Install PHPon a Windows or Linux
machine Install MySQLon a Windows or Linux
machine
Or
you can install XAMMP
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Setup and installation of XAMPP
Download XAMPP for your operatingsystem from:
www.apachefriends.org/en/xampp.html
If you are using Windows, just run theinstaller (disable proxies)
If you are using Linux, untar the package
to the appropriate directory and run:/opt/lampp/lampp start
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How do you make a PHP program?
The process is identical to how you make anHTML page, even if you use a visual tool likeDreamweaver
Create an HTML page in any editor (even
notepad will work)
Add PHP code to the page
Save in your webserver directory
opt\lampp\htdocsin Linux C:\Program Files\xampp\htdocsin Windows
View in any web browser
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PHP Syntax
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PHP Syntax
You cannot view the PHP source code byselecting "View source" in the browser -you will only see the output from the PHP
file, which is plain HTML. This is because the scripts are executed
on the server before the result is sent back
to the browser.
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Basic PHP Syntax
A PHP scripting block always startswith . A PHP scriptingblock can be placed anywhere in the document.
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Basic PHP Syntax
A PHP file normally contains HTML
tags, just like an HTML file, and somePHP scripting code.
We have an example of a simple PHPscript which sends the text "HelloWorld" to the browser.
Each code line in PHP must end with asemicolon.
The semicolon is a separator and isused to distinguish one set ofinstructions from another.
There are two basic statements tooutput text with PHP: echoand print.
In the example above we have usedthe echo statement to output the text"Hello World".
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Comments in PHP
In PHP, we use // tomake a single-linecomment or /* and */to make a large
comment block.
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Hands-on 1: Hel lo world Please open a text editor, Notepad if you are in windows
Type the follow into the text editor:
Me and PHP
Save the file as handson1.php(add quotes if you areusing Windows)
Open a web browser
Type http://localhost/handson1.php and hit
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Expected Output:
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PHP Variables
Variables are used for storing values,such as numbers, strings or function
results, so that they can be used manytimes in a script.
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Variables in PHP
All variables in PHPstart with a $ signsymbol. Variablesmay contain strings,
numbers, or arrays. In the example, the
PHP script assignsthe string "HelloWorld" to a variablecalled $txt.
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Variables in PHP
To concatenate twoor more variablestogether, use the dot(.) operator.
The output of thescript will be: "HelloWorld 1234".
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Variable Naming Rules
A variable name must start with a $ sign symboland then followed by a letter or an underscore"_"
A variable name can only contain alpha-numeric
characters and underscores (a-Z, 0-9, and _ )
A variable name should not contain spaces.
If a variable name should be more than one
word, it should be separated with underscore($my_string), or with capitalization ($myString)
H d 2
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Hands -on 2:
Exper iment ing w ith var iables
Create a PHP program with variable namedtest (remember the dollar sign). Then do thefollowing:
a. store the number 35 to test and print the
result;
b. add 10.0000 to test and print the result;
c. subtract 5.123123 from test and print it out;
d. store the character string happy to behere to test and print;
e. add 10.0000 to the variable test and print.
Save it as handson2.php, and demonstrate it.
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PHP Operators
Operators are used to operate onvalues.
This section lists the different operatorsused in PHP.
SameWith
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Arithmetic OperatorsOperator Description Example Result
+ Addition x=2x+2
4
- Subtraction x=2
5-x
3
* Multiplication x=4
x*5
20
/ Division 15/5
5/2
3
2.5
% Modulus (division
remainder)
5%2
10%8
10%2
1
2
0++ Increment x=5
x++
x=6
-- Decrement x=5
x--
x=4
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Assignment Operators
Operator Example Is The Same As
= x=y x=y
+= x+=y x=x+y
-= x-=y x=x-y
*= x*=y x=x*y
/= x/=y x=x/y
%= x%=y x=x%y
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Comparison Operators
Operator Description Example
== is equal to 5==8 returns
false
!= is not equal 5!=8 returns
true
> is greater than 5>8 returns
false
< is less than 5= is greater thanor equal to
5>=8 returnsfalse
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Logical Operators
Operator Description Example
&& and x=6
y=3
(x < 10 && y >
1) returns
true|| or x=6
y=3
(x==5 || y==5)
returns false
! not x=6
y=3
!(x==y) returns
true
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Conditional Statements
Very often when you write code, you want toperform different actions for different decisions.
You can use conditional statements in your codeto do this.
if...else statement- use this statement if youwant to execute a set of code when a conditionis true and another if the condition is not true
elseif statement- is used with the if...elsestatement to execute a set of code if oneofseveral condition are true
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The If...Else Statement
Example
The following examplewill output "Have a niceweekend!" if the currentday is Friday, otherwise it
will output "Have a niceday!":
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The If...Else Statement
If more than one line should beexecuted if a condition istrue/false, the lines should beenclosed within curly braces:
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The ElseIf Statement
Example
The following example willoutput "Have a nice weekend!"if the current day is Friday, and"Have a nice Sunday!" if thecurrent day is Sunday.
Otherwise it will output "Have anice day!":
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PHP Switch Statement
Example
This is how it works: A single expression (most
often a variable) is evaluatedonce
The value of the expression iscompared with the values foreach case in the structure
If there is a match, the codeassociated with that case isexecuted
After a code isexecuted, break is used to stop
the code from running into thenext case
The default statement is usedif none of the cases are true
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PHP Looping
Looping statements in PHP are
used to execute the same block ofcode a specified number of times.
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Looping
Very often when you write code, you want the sameblock of code to run a number of times. You can uselooping statements in your code to perform this.
In PHP we have the following looping statements: while - loops through a block of code if and as long as a
specified condition is true do...while- loops through a block of code once, and then
repeats the loop as long as a special condition is true
for - loops through a block of code a specified number of times
foreach - loops through a block of code for each element in an
array
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The while Statement
Example
The following example demonstrates a loop that will continue to run as long asthe variable i is less than, or equal to 5. i will increase by 1 each time theloop runs:
SameWith
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The do...while Statement
Example
The following example will increment the value of i at least once, and it willcontinue incrementing the variable i as long as it has a value of less than 5:
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The for Statement
Example
The following example prints the text "Hello World!" five times:
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Hands-on 3: Loop
Write a PHP program and create a variablenamed $age. Using control structures, test $age.
a. If $age is less than 18, it should print novote.
b. If $age is greater than or equal to 18, itshould print vote.
c. Using a loop of your choice, make the
program print happy birthday $age times (so if $age is 15, it will print 15 times)
Save it as handson3.php, and demonstrate it.
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PHP Arrays
An array can store one or more
values in a single variable name.
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What is an array?
When working with PHP, sooner or later, youmight want to create many similar variables.
Instead of having many similar variables, youcan store the data as elements in an array.
Each element in the array has its own ID so thatit can be easily accessed.
There are three different kind of arrays: Numeric array- An array with a numeric ID key Associative array- An array where each ID key
is associated with a value Multidimensional array- An array containing
one or more arrays
N i A
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Numeric ArraysA numeric array stores each element with a numeric ID key.There are different ways to create a numeric array.
Example 1In this example the ID key is automatically assigned:
$names = array("Peter","Quagmire","Joe");
Example 2In this example we assign the ID key manually:
$names[0] = "Peter";$names[1] = "Quagmire";$names[2] = "Joe";
The ID keys can be used in a script:
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Associative ArraysAn associative array, each ID key is associated with a value.With associative arrays we can use the values as keys and assign values to them.
Example 1In this example we use an array to assign ages to the different persons:
$ages = array("Peter"=>32, "Quagmire"=>30, "Joe"=>34);
Example 2This example is the same as example 1, but shows a different way of creating the array:
$ages['Peter'] = "32";$ages['Quagmire'] = "30";$ages['Joe'] = "34";
The ID keys can be used in a script:
The code above will output:Peter is 32 years old.
M ltidi i l A
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Multidimensional Arrays
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. Example In this example we create a multidimensional array, with
automatically assigned ID keys:
$families = array("Griffin"=>array("Peter","Lois",Megan"),"Quagmire"=>array("Glenn"),"Brown"=>array("Cleveland","Loretta","Junior")
);
echo value is.$families[Brown][1];
M ltidi i l A
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Multidimensional Arrays
The array above would look like this if written to the output:
Array([Griffin] => Array([0] => Peter[1] => Lois[2] => Megan
)[Quagmire] => Array([0] => Glenn)
[Brown] => Array(
[0] => Cleveland[1] => Loretta[2] => Junior)
)
Th f h St t t
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The foreach Statement
The foreach statement is
used to loop through arrays. For every loop, the value of
the current array element isassigned to $value (and thearray pointer is moved by
one) - so on the next loop,you'll be looking at the nextelement.
Example
The following exampledemonstrates a loop that willprint the values of the givenarray.
H d 4 A
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Hands-on 4: Array
Write a PHP program and create an arrayof 10 integers named $array_of_scores.Using control structures, do the following:
a. Print all the integers. b. Get the sum of all the integers and print;
c. Among the integers, count the number
of odd and even integers, then, print;
Save it as handson4.php, and demonstrate it.
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PHP Functions
The real power of PHP comes from itsfunctions.
In PHP - there are more than 700 built-in functions available.
C t PHP F ti
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Create a PHP Function
A function is a block of code that can be executedwhenever we need it.
Creating PHP functions:
All functions start with the word "function()"
Name the function - It should be possible to understandwhat the function does by its name. The name can startwith a letter or underscore (not a number)
Add a "{" - The function code starts after the openingcurly brace
Insert the function code
Add a "}" - The function is finished by a closing curlybrace
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Create a PHP Function
Example
A simple function that writes my name when it is called:
U PHP F ti
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Use a PHP Function
Now we will use the function in a PHP script:
The output of the code above will be:
Hello world!My name is Kai Jim Refsnes.That's right, Kai Jim Refsnes is my name.
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PHP Functions Addingparameters
Our first function (writeMyName()) is a verysimple function. It only writes a static string.
To add more functionality to a function, we canadd parameters.
A parameter is just like a variable.
You may have noticed the parentheses after thefunction name, like: writeMyName().
The parameters are specified inside theparentheses.
PHP Functions - Adding
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PHP Functions Addingparameters
Example 1
The following example will writedifferent first names, but the samelast name:
The output of the code above willbe:
My name is Kai Jim Refsnes. My name is Hege Refsnes. My name is Stale Refsnes.
PHP Functions - Adding
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PHP Functions Addingparameters
Example 2
The following function has twoparameters:
The output of the code above willbe:
My name is Kai Jim Refsnes.
My name is Hege Refsnes! My name is Stle Refsnes...
PHP F ti R t l
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PHP Functions - Return values
Functions can also be used to return values.
Example
The output of the code above will be:
1 + 16 = 17
Hands on 5: Functions
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Hands-on 5: Functions
Write a PHP program and create the followingfunctions:
a. description(): print any statement to describe yourbest body feature, asset, or talent;
b. function to print the array of integers (fromhandson4).
Save it as handson5.php, and demonstrate it.
Online References
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Online References.
To help you work with the activity, you canaccess the following online PHP tutorials:
a. http://www.tizag.com/phpT
b. http://www.learnphp-tutorial.com c. http://www.killerphp.com/videos/
d. http://www.w3schools.com
e. any other online PHP tutorials.
http://www.tizag.com/phpThttp://www.learnphp-tutorial.com/http://www.killerphp.com/videos/http://www.killerphp.com/videos/http://www.learnphp-tutorial.com/http://www.learnphp-tutorial.com/http://www.learnphp-tutorial.com/http://www.tizag.com/phpT