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)) . '/-';

[admin]

Post example links, experiment (best way to learn) and discuss. No cut and paste please. Type the examples yourself, make mistake, try to fix it yourself, , think, refer back, post you code, so others can fix it for you. Lean from your mistakes (or others).

[sherlyk]

http://php.flashwebhost.com/sherly/add.php

<?php

$M = 20;
$N = 50;
echo $M + $N;

[admin]

http://php.flashwebhost.com/sherly/add.php

<?php

$M = 20;
$N = 50;
echo $M + $N;

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

It is ok, but better use descriptive names for variables. One letter variable names can be confusing in most cases.

[annie]

I got an error while adding break in http://php.flashwebhost.com/annie/company.php

Parse error:  syntax error, unexpected '>' in /home/fwhphp/public_html/annie/company.php on line 3 

 <?php
$companyname = 'Relience';
echo $companyname <br> ; 
$companyname = 'Whirpool'; 
echo $companyname ;

[sherlyk]

I got an error http://php.flashwebhost.com/sherly/name.php

Parse error:  syntax error, unexpected '' ;' (T_ENCAPSED_AND_WHITESPACE), expecting ',' or ';' in /home/fwhphp/public_html/sherly/name.php on line 7

<?php
$my_string = 'Hi Meera. My anme is Neena';
$my_number = 8;
$my_letter = N;
echo $my_string;
echo $my_number;
echo $my_letter' ;

[admin]

I got an error while adding break in http://php.flashwebhost.com/annie/company.php

Parse error:  syntax error, unexpected '>' in /home/fwhphp/public_html/annie/company.php on line 3 

 <?php
$companyname = 'Relience';
echo $companyname <br> ; 
$companyname = 'Whirpool'; 
echo $companyname ;

Problem is on line number 3.

echo $companyname <br> ;

To fix, replace that line with

echo $companyname .  '<br>' ;

$companyname is a variable. We use DOT to join it with string <br>. String should start with a quote, end with a quote.

As for variable name, proper naming convention is $companyName, because it is two words, and easy to read.


Fixed code

<?php

$companyName = 'Relience';

echo $companyname .  '<br>'; 

// here we store another text to same variable $companyName
$companyName = 'Whirpool'; 

echo $companyname ;

[annie]

http://php.flashwebhost.com/annie/day_2_variables_3.php

 
<?php
$name = 'George';
$Rank = 1;
$Mark = 800;
$School = 'Raja Giri Public School';
echo $name . ' from ' . $School . ' got Rank ' . $Rank . ' He have ' . $Mark . 'Marks';

[Austinwhite]

I got an error while adding break in http://php.flashwebhost.com/annie/company.php

Parse error:  syntax error, unexpected '>' in /home/fwhphp/public_html/annie/company.php on line 3 

 <?php
$companyname = 'Relience';
echo $companyname <br> ; 
$companyname = 'Whirpool'; 
echo $companyname ;

Use a concat operator after $companyname and also put the <br> in quotes ($companyname.'<br>'; )

<?php$companyname = 'Relience';
echo $companyname.'<br>'; 
$companyname = 'Whirpool'; 
echo $companyname ;

[melbin]

I got an error while adding break in http://php.flashwebhost.com/annie/company.php

Parse error:  syntax error, unexpected '>' in /home/fwhphp/public_html/annie/company.php on line 3 

 <?php
$companyname = 'Relience';
echo $companyname <br> ; 
$companyname = 'Whirpool'; 
echo $companyname ;

Doubt 1
Is it possible to use same variable name for multiple values ?

Doubt 2
Is variable name is case sensitive ?

I mean both the following variables will give different values in the same script ?

$variableName
$variablename