PHP Study Group

Chapter Four (exercise one)

Adding, Subtracting, Multiplying, and Dividing

This exercise performs various calculations based on an e-commerce situation.
It takes $quantity, $price, $tax, $shipping,
and $discount values and generates a $total cost.
This $total value is then divided by the number of $payments
to generate a monthly expense $total value.

Chapter Four (exercise two)

Formatting Numbers

<?php

/* number_format() works like round()

with added commas. */

$total = number_format ($total, 2);

$monthly = number_format ($monthly, 2);

round ($total, 2);//rounds total to 2 decimal places

?>

Chapter Four (exercise three)

Using Multiple Operators

Reference:
$total = $price * $quantity;
$total = $total + $shipping;
$total = $total - $discount;

$taxrate = $tax/100;
$taxrate = $taxrate + 1;

Change the way $total is calculated:
$total = (($price * $quantity) + $shipping) - $discount;

Change the way $taxrate is calculated:
$taxrate = ($tax/100) + 1;

Chapter Four (excercise four)

Incrementing and Decrementing a Number

Reference:
$taxrate = ($tax/100) + 1;
Change the way $taxrate is incremented:
$taxrate = $tax/100; // Value divided by 100
$taxrate++;// Increment this value by 1
Example:
$var = 10; // 10
$var++; // 11
$var--; // Returns to 10

Fill out this form to calculate the total cost:

• Price:
• Quantity:
• Discount:
• Tax:
• Shipping method: Slow and steady Put a move on it
• Number of payments to make:

Chapter Four (exercise five)

Creating Random Numbers

And last but not least...
The lucky 3 digit Ohio Lottery numbers are: 255

Chapter Five (exercise one)

Connecting Strings

Use the period to concatenate strings formally to understand what is occurring in the code:
$s1 = ' Hello'; // One space before
$s2 = ' World '; // One space before and after
$greeting = $s1 . $s2;
print $greeting; // Has the same output as
print $s1$s2; // Variables side by side
Output: ( Hello World ) // One space between. One space before and after
print $s1 $s2; // Variables separated
Output: ( Hello  World ) // Two spaces between. One space before and after.

Chapter Five (exercise two)

Combating Magic Quotes

If Magic Quotes are enabled (mine are) than any quotes entered into a form field will display the output with backslashes to escape the quotes.

Using the stripslashes() function will remove these escapes after the variable is created and before the variable is printed.
Example:
$name = $_POST['name'];
$name = stripslashes ($name);
print $name;
Same Output Example:
// This example strips the string after the variable has been posted
$name = stripslashes ($_POST['name']);

If Magic Quotes are disabled and you want an output code to escape slashes, use the addslashes() function.

Chapter Five (exercise three)

Encoding and decoding strings.

The urlencode() function encodes and passes the a string variable to the next page.
No need for htmlentities() or strip_tags().

Values are are URL-encoded before being sent and then decoded into the follow-up page.

Chapter Five (exercise four)

Replacing parts of a string.

Example:
$posting = str_replace ('forum', 'Hello World Forum', $posting);
Replaces the word (forum) if entered in the posting field with (Hello World Forum).

Can also be used to remove offensive language and in multiple lines.

Chapter Five (exercise five)

Tokenizing, Searching, and Comparing Strings.

Example:
Use the strtok() function to create a substring referred to as a token from a larger string.
$title = strtok($recipe, 'submitted');
Using this code I could pull out a string from a recipe and name it $title before it reaches the word 'submitted'.
So, if all recipes as $recipe began with the Title followed by (Submitted by) then I could pull the title from the recipe.

The substr() function is used to find and print the position of a string.
$fourDigitPassword = substr($password,0,4);

Also see,
strstr() and strpos()

Chapter Five (exercise six)

Other string functions.

The trim() function trims spaces before and after strings but not in between.
Also see, rtrim() and ltrim().
Use the ucfirst() function to capitalize the first letter of a string.
The ucwords() function capitalizes the start of every word in a string.
The strtoupper() prints in all uppercase letters.
Use strtolower() to print all lowercase letters.

For names, first convert the string to lowercase using the strtolower() function.
Then, add the ucwords() function to capitalize each new word (in this case Name).
$name = strtolower ($name);
$name = ucwords ($name);

Example:
$name = ucwords (strtolower($name)); // From right to left. First lower, then replace.

Please complete this form to submit your posting:

• First Name:
• Last Name:
• Email Address:
• Posting:
  

Chapter Six

Control Structures

The IF Conditional Statement controls how a variable is passed.
Using the empty() function can avoid errors when a variable is not defined.
Curly brackets are used when a conditional statement covers more than one line.

The form below uses comparison operators to check if the passwords entered in the fields match by using the two variables, $password and $confirm like this:
if ($password != $confirm) { // I think of the operator != as (does not equal to).
print '...does not match';

The Switch Conditional is my favorite part of this chapter's lessons.
It uses the value of the variable for each Case.

The For Loop is a bit tricky as I've learned in previous experiences.
// The loop below shows that the value of $i starts at 1 (default is 0).
// $i <= 10; The value of $i is less than or equal to 10.
// $i++ (mathematical operator) increases the value of $i by 1 for every loop.
for($i = 1; $i <= 10; $i++) {
print "$i ";
}

Please complete this form to register:

• First Name:
• Last Name:
• Email Address:
• Password:
• Confirm Password:

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