Day 2 - Variables - Become PHP Expert in 30 days

[admin]

Variables

Variables are used to store data (String, Numbers, etc..) in a program.



In PHP, variables start with symbol $. Examples for variable name

$name
$companyName 

It is always better to use descriptive name for variables, so you know what is stored in a variable. For example, to store mark, we use variable $mark

$mark = 100; // Good
$m1 = 100; // Bad, it will work but $m1, how we know what is stored in it ? It can be anything. 

In above example, we stored numeric value in variable. When storing numeric value, we don't use quotes.

Lets have some string variable

$name = 'Batman';
$companyName = 'FlashWebHost.com'; 

Now lets have some real PHP examples

day_2_variables_1.php

<?php

$companyName = 'FlashWebHost.com';

echo  $companyName;

Now lets make it little more friendly with PHP string concatenation, that is joining two strings.

day_2_variables_2.php

<?php

$companyName = 'FlashWebHost.com';

echo  'Welcome to ' . $companyName;

day_2_variables_3.php

Another example with string and numeric variables.

<?php

$name = 'Raju';
$rank = 1;
$mark = 1000;
$school = 'LP School';

echo  $name . ' from ' . $school . ' got rank ' . $rank . '. He have ' . $mark . ' marks.';

Back to School, some simple maths

Here are some basic numeric operations using PHP

day_2_variables_4.php

<?php

$numCats = 10;
$numDogs = 20;

echo 'Total number of animals ' . ($numCats + $numDogs);

day_2_variables_5.php

In this example we use multiplication operator in PHP to multiply 2 numbers.

<?php

$costOfApple = 12.00;
$numApple = 8;

echo 'Cost of ' . $numApple . ' apples = Rs: ' . ($numApple * $costOfApple) . '/-';

day_2_variables_6.php

Lets do some billing.

<?php

$webhosting_price = 399;
$domain_price = 500;
$discount = 0.1; // 10% discount.

echo 'Total cost = Rs: ' . ($webhosting_price + $domain_price) . '/-';
echo '<br>';echo 'Price After discount = Rs: ' . ( ($webhosting_price + $domain_price) -  (($webhosting_price + $domain_price) *  $discount)) . '/-';

That is lot of brackets, and repeated maths operation ($webhosting_price + $domain_price repeated 3 times), that is not efficient, lets simplify the code.

day_2_variables_7.php

Following code do exactly same as day_2_variables_6.php, but we added extra variable $total_cost, that store the value of $webhosting_price + $domain_price.

<?php

$webhosting_price = 399;
$domain_price = 500;
$discount = 0.1; // 10% discount.
$total_cost = $webhosting_price + $domain_price;

echo 'Total cost = Rs: ' . $total_cost . '/-';echo '<br>';
echo 'Price After discount = Rs: ' . ( $total_cost -  ($total_cost *  $discount)) . '/-';