CPAP.com Introduction To Coding: Part 2

Introduction To Coding
Part Deuce
Jeremy Montoya

What Will Be Covered?
●General overview of last session
(variables, if statements, etc..) but from the
PHP aspect
● Understand how logic and concepts can
be learned – and easily applied using any
language.
● A high level overview of querying a
database using PHP

No SQL again today..
●That concept is a completely
different monster in the world of
programming.

Today's Language - PHP
PHP Hypertext Processor
● One of the most widely used server
scripting languages
● Ideal to use when a web page needs
to be dynamic or when communication
with databases is needed
● Static pages can be generated as well
– but not needed

Where Is This PHP?
● Windows
http://windows.php.net/download/
● Unix
http://www.php.net/manual/en/install.unix.php
● Mac OS X
http://www.php.net/manual/en/install.macosx.php

Not Everyone Likes PHP..
(11:39:56 AM) Myself: do you like PHP
(11:40:04 AM) Paimoe: eh
(11:40:17 AM) Myself: congrats
(11:40:20 AM) Myself: you just made my presentation
(11:40:24 AM) Paimoe: lol

Some People Do!
(11:44:09 AM) Myself: do you like PHP
(11:44:15 AM) Ben: I do
(11:44:18 AM) Myself: why's that
(11:44:18 AM) Ben: It works well enough
(11:44:24 AM) Ben: Some useful features
(11:44:28 AM) Ben: Stellar documents
(11:44:33 AM) Myself: congrats, you just made my
presentation
(11:44:41 AM) Ben: lol

Today's Learning Process
PHP Edition
● Variables
● Storage
● Comments
● Running Code
● Review and Run
● If/Else Statement
● Loops
● Exercises
● Database Interaction
●“The Knockout” Recipe

PHP Syntax
Instruction separation
PHP requires semicolons to be used to separate
instructions (Ruby does not)
Ex:
$a = “test”; $b = “another test”;
Commenting
While Ruby uses the pound sign to tell the computer
to ignore lines of code, PHP uses slashes and
asterisks for comments.
For Single Line Comments (Double Slash)
//This is a commented line
$testvar = “hello”;

PHP Syntax (cont.)
There may be instances where one may want to
comment out a whole section of code, rather than a
single line. This normally happens when testing
different sections or describing a function (multiple
sentences needed). To do this, start the commented
area with “/*” and close it off with “*/”.
/*
This next line will assign the value 7 to a variable
because 7 is my favorite number. If anyone wants to
know why, they can come and ask me.
*/
$var = 7;

PHP Variables
Syntax: $<variable name>
● Must start with a dollar sign
Ex: $firstname = “Jeremy”;
Variable Name
● Variable name must begin with a letter or “_”
(underscore)
Ex:
$_fruit = “pear”; //Good
$8mile = “slimshady”; //Bad
● Variable can only contain alphanumeric characters
and “_”, no spaces allowed, case sensitive ($test !=
$Test)

PHP Variables (Cont.)
● Same method of assigning strings, integers as
Ruby has – only slightly different syntax.
Ruby
A = “apple”
B = 10
PHP
$A = “apple”;
$B = 10;
Remember, PHP requires semicolons to be used to
separate out instructions

PHP Variables (Cont.)
● As with Ruby, storage actions are done the same
way, with just a few syntax differences.
Ruby
Three = one + two
Fullname = “Jeremy Montoya”
PHP
$three = $one + $two;
$fullname = “Jeremy Montoya”;

Running a PHP script
● Without performing the full installation and just learning
the syntax. Simply type in your script and submit to see
the output.
http://sandbox.onlinephpfunctions.com/
● For full implementation / ability to see graphical output,
a .php file will need to be created, with the code written
inside the file. (Ruby = .rb, PHP = .php)
● With your .PHP file saved (assuming you have
performed the steps needed to have PHP installed,
alongside a web server (apache, IIS, etc..), simply place
the file in your web directory and access through the
browser.
Ex: http://www.cpap.com/index.php

Review and Run!
http://sandbox.onlinephpfunctions.com/

If/Else Statements
Review
● There may be scenarios where we want to perform
certain actions depending on the value of a variable.
This is where If/Else statements come into place.
Ex:
if( $pet == “cat” ){
echo “How unfortunate!”;
}
else{
echo “Good choice”;
}

If/Else Statements
● Once again, logic is the same, only with syntax
differences.
Ruby
If one == 2
puts “equals 2”
else
puts “does not equal 2”
end
PHP
if( $one == 2 ){
echo “equals 2”;
}
else{
echo “does not equal 2”;
}

Loops
● Used in programming to execute a block of code a
given number of times, or while a condition is true.
● There are a number of different types of loops to
use, all which have advantages depending on the
task at hand.
● These would include for and while loops

Loop Scenario
Let us imagine we would want to write a piece of
code that is to be used during the final moments of
2013. We would like a countdown to be displayed to
the crowd starting at 10 seconds until midnight. Once
midnight is reached, a large “HAPPY NEW YEAR!”
message will be displayed.

For Loops
For our “Happy New Year” task...it would look like
this in PHP:
for( $i=10; $i > 0; $i=$i-1 ){
echo $i;
}
echo “HAPPY NEW YEAR!”;
For loops are constructed different parts, which we
will go over in the next several slides.

For Loops
for( $i=10; $i > 0; $i=$i-1 ){
echo $i;
}
The first part of the loop is the first instruction to be
run, before the loop even starts.
Typically, it assigns the starting value to the variable
involved in the loop. In the New Year's scenario, it's
starting the counter of at 10 (since we going to be
counting down until 0.

For Loops
for( $i=10; $i > 0; $i=$i-1 ){
echo $i;
}
The second part of the loop is the condition that is
checked on every iteration through the loop. It is the
deciding factor in terms of knowing when to stop
looping and when to keep going.
In the New Year's scenario, the condition is to
continue the loop while the variable $i is greater than
0. Once that condition is violated ($i is equal to 0),
then the loop stops.

For Loops
for( $i=10; $i > 0; $i=$i-1 ){
echo $i;
}
The third part of the loop is the instruction to be done
after each iteration of loop. It's the most important
part due to the fact it controls the variable finally
getting to an end condition ($i reaching 0).
In the New Year's scenario, the instruction is to
deduct 1 from $i after each iteration since we are
counting down.

For Loops
for( $i=10; $i > 0; $i=$i-1 ){
echo $i;
}
echo “HAPPY NEW YEAR”;
The section that lies within the open and close
brackets is the block of code that is to be executed
on each iteration.
In this scenario, we wanted to display a countdown,
so we will simply be displaying out the value of $i to
the screen to emulate this.

Cat Break:
what what what what, scratch scratch scratch, meow meow meow

For Loops
for( $i=10; $i > 0; $i=$i-1 ){
echo $i;
}
echo “HAPPY NEW YEAR”;
As soon as the value of $i reaches 0, the condition
“$i > 0” will be violated, thus exiting out of loop. Now,
we will see our final message which is set to show
after the loop has completed.

DANGER: For Loops
for( $i=10; $i > 0; $i=$i-1 ){
echo $i;
$i = $i + 5;
}
10
15
14
As with any loops, one must be sure to carefully set up their loop parameters
correctly, as well as not manipulating the loop variable within the block of code.
In this case, everything is setup properly, except for a single line that will add 5
to $i during each iteration. This now causes $i to just get bigger and bigger,
rather than closer to 0. This will result in what we call an “infinite loop”.

While Loop
Similar to for loops, but with a different structural
setup. In many cases, this will be used when the
number of iterations is not known. Generally, there
will be a condition that must be met to terminate the
loop. In this example, we'll play the guessing game.
$numberInHead=8;
$guess=0;
while( $guess != $numberInHead ){
//ask the user for a number
}
echo “ABOUT TIME!”;
As you can notice, it took a couple more lines of
code to achieve what the for loop did, but in many
cases, it's easier to read for someone else.

While Loop
$numberInHead=8;
$guess=0;
}
This acts just like the first parameter in a for loop.
We want to start the variable off at it's start value, so
we set it to 0 since no guess has been made.

While Loop
$numberInHead=8;
$guess=0;
//ask the user for a number....
$guess = whateverweaskthemfor;
}
The core of a while loop. One can pretty much say
what they see out loud to understand what's
happening. “While variable 'guess' is not equal to the
variable $numberInHead”, we will perform whatever
is in between the brackets.

While Loop
$numberInHead=8;
$guess=0;
}
Just like the for loop, any code within the brackets
will be executed on each iteration. In this case, we
will prompt the user for a number to guess.

While Loop
$numberInHead=8;
$guess=0;
}
Alas, the user will finally make the correct guess, and
get out of the loop. We can then congratulate them
accordingly.

What Will Be Output To The
Screen?
for($x=0;$x<=10;$x=$x+1){
if( $x < 5 ){
echo $x;
}
else{
echo “$x is too high”;
}
}
echo “Done!”;

What Will Be Output To The
Screen?
for($x=0;$x<=10;$x=$x+1){
if( $x < 5 ){
echo $x;
}
else{
echo “$x is too high”;
}
}
echo “Done!”;
0
1
2
3
4
5 is too high
6 is too high
7 is too high
8 is too high
9 is too high
10 is too high

What's Wrong With This Loop?
for( $i=0; $i<5; $i=$i-1 ){
echo “Hooray for coding”;
}

for( $i=0; $i<5; $i=$i-1 ){
echo “Hooray for coding”;
}
$i will start at 0 and decrement
by 1 each time, thus never
satisfying the condition to exit
the loop, which is for $i to
exceed or equal 5.
INFINITE LOOP!

x = 5;
while( x > 0 ){
x = x – 1;
}

x = 5;
while( x > 0 ){
x = x - 1;
}
Shame on you if you didn't get it. This is PHP, where
are all the dollar signs?!!

Database Interaction
Now that we have gotten basic condition
checking and loops out of the way in PHP, we
can now go over how we use this when talking to
databases.

Database Interaction
As a starting example, let's say we have a table named
“PlacesTbl” of restaurants in the local area that a group
enjoys going to for lunch. It consists of 3 fields - a unique
id given to each one, the name of the restaurant and a
flag implying if they have gluten free options or not.

Database Request
A page needs to be set up to display to users all the restaurants in the area - in order of
the restaurants name, and stating whether or not they are gluten free. The SQL statement is
the first thing to set up.
SELECT *
FROM PlacesTbl
ORDER BY Description
Running this SQL manually before using in your PHP script
should always be done so you know it's working correctly.

PHP Implementation
Now that we have our SQL statement set up, it's now time to add it into a PHP
script and perform the logic to read through the results, and output accordingly.
$getPlaces =
“SELECT *
FROM PlacesTbl
ORDER BY Description”;
$resultPlaces = ConnectToDatabase( $getPlaces );
This first part of the script assigned the SQL statement to a variable, and then
issue a call to the function which expects an SQL query to be passed over, and
in turn - makes the call to the database with it and returns the result. In this
case, the result is placed in a variable called $resultPlaces.
Note: ConnectToDatabase should just be viewed as a function that exists that
simply will expect an SQL query and will return the results upon calling the
database. There is a more in depth topic to go into to explain this.

PHP Implementation
With $resultPlaces containing the result of our query, it's now time to read
through it and output the information.
$rowPlaces = mysql_fetch_array( $resultPlaces );
while( $rowPlaces != false ){
if( $rowPlaces['FlagGF'] == 1 ){
echo $rowPlaces['Description'] . “ - Gluten Free<br>”;
}
else{
echo $rowPlaces['Description'] . “ - Gluten Everywhere<br>”;
}
//Get next row
}
Ok, first let's explain the mysql_fetch_array function call. This is a function built
into the MySQL library in PHP. It receives in the variable that is holding the
result, and returns the next row in the results. If there are no rows left to read in,
it returns false.
Given that we will set our loop variable to the first row and begin the loop.

PHP Implementation
}
else{
echo $rowPlaces['Description'] . “ - Gluten Everywhere<br>”;
}
//Get next row
}
We will set the condition to get out of our loop to be once $rowPlaces is set to
false. This is because once we run out of rows to read, mysql_fetch_array will
return false.

PHP Implementation
}
else{
echo $rowPlaces['Description'] . “ - Gluten
Everywhere<br>”;
}
//Get next row
}
In the meat of our loop, we will perform a comparison to see if the gluten free
flag (“FlagGF”) is set to 1. If it is, the restaurants name will be output, alongside
text stating it is gluten free. If it is not equal to 1, we will perform the same
output - but stating it's full of gluten.
After the output is displayed, we will give our loop variable $rowPlaces its new
value, by assigning it what mysql_fetch_array now returns. This will prepare it
for the condition check at the beginning of the loop!

PHP Implementation
The resulting page will look something like this!

The Knockout
Perfect for inducing an idyllic summer nap, The Knockout offers a sweet blend of fruit
with a sharp kick of tequila:
2 parts lime juice
1 part tequila
1 part Midori
splash of simple syrup
8 blueberries
Crush blueberries in a bowl with a spoon. Set aside.
Combine lime juice, tequila, midori and simple syrup in a tumbler with ice. Shake.
Salt serving glass, fill with ice, garnish with blueberries, then pour the strained mixture
on top.
Garnish with a blueberries and a sprig of mint.
And what do you get...?

CPAP.com Introduction To Coding: Part 2

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CPAP.com Introduction To Coding: Part 2