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PHP with MySQL Essential Training
Illustration by Don Barnett

Numbers part two: Floating points


From:

PHP with MySQL Essential Training

with Kevin Skoglund

Video: Numbers part two: Floating points

Now we've taken a look at integers, I'm going to to take a look at another type of number which are floating point numbers also simply called Floats, for short. You may know them more commonly as decimal numbers. That is numbers that have a decimals in them followed by a number of significant digits 2.75 is an example of a floating point number. Now, it may seem arbitrary to you if you haven't done a lot of programming before that we divide numbers into these two types. Integers and floating point, and the reason why is because computers store integers and floating points in different ways in memory.
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  1. 4m 8s
    1. Welcome
      1m 0s
    2. Using the exercise files
      3m 8s
  2. 15m 6s
    1. What is PHP?
      3m 52s
    2. The history of PHP
      2m 51s
    3. Why choose PHP?
      4m 10s
    4. Installation overview
      4m 13s
  3. 54m 53s
    1. Overview
      2m 33s
    2. Working with Apache Web Server
      6m 56s
    3. Changing the document root
      7m 24s
    4. Enabling PHP
      6m 16s
    5. Upgrading PHP
      3m 30s
    6. Configuring PHP
      10m 3s
    7. Installing MySQL
      5m 46s
    8. Configuring MySQL
      7m 24s
    9. Text editor
      5m 1s
  4. 31m 25s
    1. Overview
      3m 27s
    2. Installing WampServer
      5m 46s
    3. Finding the document root
      2m 24s
    4. Configuring PHP
      8m 12s
    5. Configuring MySQL
      5m 45s
    6. Text editor
      5m 51s
  5. 19m 12s
    1. Embedding PHP code on a page
      6m 43s
    2. Outputting dynamic text
      5m 55s
    3. The operational trail
      2m 27s
    4. Inserting code comments
      4m 7s
  6. 1h 18m
    1. Variables
      7m 50s
    2. Strings
      4m 38s
    3. String functions
      8m 54s
    4. Numbers part one: Integers
      6m 27s
    5. Numbers part two: Floating points
      5m 25s
    6. Arrays
      10m 0s
    7. Associative arrays
      6m 37s
    8. Array functions
      6m 33s
    9. Booleans
      3m 50s
    10. NULL and empty
      5m 15s
    11. Type juggling and casting
      8m 27s
    12. Constants
      4m 43s
  7. 27m 37s
    1. If statements
      6m 0s
    2. Else and elseif statements
      4m 16s
    3. Logical operators
      7m 30s
    4. Switch statements
      9m 51s
  8. 42m 15s
    1. While loops
      8m 41s
    2. For loops
      5m 59s
    3. Foreach loops
      8m 16s
    4. Continue
      8m 28s
    5. Break
      4m 8s
    6. Understanding array pointers
      6m 43s
  9. 37m 25s
    1. Defining functions
      8m 25s
    2. Function arguments
      5m 32s
    3. Returning values from a function
      7m 33s
    4. Multiple return values
      4m 53s
    5. Scope and global variables
      6m 2s
    6. Setting default argument values
      5m 0s
  10. 20m 18s
    1. Common problems
      3m 47s
    2. Warnings and errors
      8m 36s
    3. Debugging and troubleshooting
      7m 55s
  11. 57m 57s
    1. Links and URLs
      5m 33s
    2. Using GET values
      5m 35s
    3. Encoding GET values
      8m 41s
    4. Encoding for HTML
      9m 26s
    5. Including and requiring files
      7m 40s
    6. Modifying headers
      6m 45s
    7. Page redirection
      6m 43s
    8. Output buffering
      7m 34s
  12. 1h 3m
    1. Building forms
      7m 28s
    2. Detecting form submissions
      5m 59s
    3. Single-page form processing
      7m 57s
    4. Validating form values
      10m 40s
    5. Problems with validation logic
      9m 54s
    6. Displaying validation errors
      7m 23s
    7. Custom validation functions
      6m 28s
    8. Single-page form with validations
      7m 25s
  13. 28m 5s
    1. Working with cookies
      2m 49s
    2. Setting cookie values
      5m 55s
    3. Reading cookie values
      6m 1s
    4. Unsetting cookie values
      4m 51s
    5. Working with sessions
      8m 29s
  14. 48m 39s
    1. MySQL introduction
      6m 43s
    2. Creating a database
      7m 41s
    3. Creating a database table
      7m 42s
    4. CRUD in MySQL
      5m 48s
    5. Populating a MySQL database
      7m 32s
    6. Relational database tables
      6m 40s
    7. Populating the relational table
      6m 33s
  15. 56m 4s
    1. Database APIs in PHP
      4m 51s
    2. Connecting to MySQL with PHP
      7m 45s
    3. Retrieving data from MySQL
      8m 47s
    4. Working with retrieved data
      6m 12s
    5. Creating records with PHP
      6m 58s
    6. Updating and deleting records with PHP
      9m 6s
    7. SQL injection
      3m 5s
    8. Escaping strings for MySQL
      6m 45s
    9. Introducing prepared statements
      2m 35s
  16. 35m 58s
    1. Blueprinting the application
      7m 19s
    2. Building the CMS database
      5m 14s
    3. Establishing your work area
      4m 38s
    4. Creating and styling the first page
      4m 22s
    5. Making page assets reusable
      6m 36s
    6. Connecting the application to the database
      7m 49s
  17. 32m 49s
    1. Adding pages to the navigation subjects
      5m 58s
    2. Refactoring the navigation
      6m 7s
    3. Selecting pages from the navigation
      6m 2s
    4. Highlighting the current page
      5m 26s
    5. Moving the navigation to a function
      9m 16s
  18. 1h 45m
    1. Finding a subject in the database
      9m 48s
    2. Refactoring the page selection
      10m 52s
    3. Creating a new subject form
      6m 55s
    4. Processing form values and adding subjects
      11m 20s
    5. Passing data in the session
      9m 16s
    6. Validating form values
      9m 40s
    7. Creating an edit subject form
      8m 30s
    8. Using single-page submission
      7m 44s
    9. Deleting a subject
      9m 44s
    10. Cleaning up
      10m 37s
    11. Assignment: Pages CRUD
      4m 30s
    12. Assignment results: Pages CRUD
      6m 10s
  19. 39m 26s
    1. The public appearance
      8m 52s
    2. Using a context for conditional code
      11m 37s
    3. Adding a default subject behavior
      6m 9s
    4. The public content area
      5m 51s
    5. Protecting page visibility
      6m 57s
  20. 1h 3m
    1. User authentication overview
      4m 3s
    2. Admin CRUD
      8m 41s
    3. Encrypting passwords
      7m 26s
    4. Salting passwords
      5m 42s
    5. Adding password encryption to CMS
      11m 54s
    6. New PHP password functions
      3m 13s
    7. Creating a login system
      11m 28s
    8. Checking for authorization
      5m 48s
    9. Creating a logout page
      5m 40s
  21. 2m 4s
    1. Next steps
      2m 4s

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PHP with MySQL Essential Training
14h 24m Beginner Jun 04, 2013

Viewers: in countries Watching now:

PHP is a popular, reliable programming language at the foundation of many smart, data-driven websites. This comprehensive course from Kevin Skoglund helps developers learn the basics of PHP (including variables, logical expressions, loops, and functions), understand how to connect PHP to a MySQL database, and gain experience developing a complete web application with site navigation, form validation, and a password-protected admin area. Kevin also covers the basic CRUD routines for updating a database, debugging techniques, and usable user interfaces. Along the way, he provides practical advice, offers examples of best practices, and demonstrates refactoring techniques to improve existing code.

Topics include:
  • What is PHP?
  • Installing and configuring PHP and MySQL
  • Exploring data types
  • Controlling code with logical expressions and loops
  • Using PHP's built-in functions
  • Writing custom functions
  • Building dynamic webpages
  • Working with forms and form data
  • Using cookies and sessions to store data
  • Connecting to MySQL with PHP
  • Creating and editing database records
  • Building a content management system
  • Adding user authentication
Subjects:
Developer Servers Programming Languages Web Development
Software:
MySQL PHP
Author:
Kevin Skoglund

Numbers part two: Floating points

Now we've taken a look at integers, I'm going to to take a look at another type of number which are floating point numbers also simply called Floats, for short. You may know them more commonly as decimal numbers. That is numbers that have a decimals in them followed by a number of significant digits 2.75 is an example of a floating point number. Now, it may seem arbitrary to you if you haven't done a lot of programming before that we divide numbers into these two types. Integers and floating point, and the reason why is because computers store integers and floating points in different ways in memory.

Mostly because of those significant digits that we have to keep track of with floating points. Because of that, almost every single programming language has two different types to work with integers and floating point numbers. So let's look at how PHP works with floats. So, I'm going to start by opening up basic.html, and then I'll just do a Save As on that. And let's just change this to be floats.php and save it in our sandbox. We'll call this floating point numbers. And let's create our first floating point number here. So, inside the PHP tags, I'm going to have echo $float equals 3.14.

That is an example of a floating point number. And floating points interact just fine with our integers. So for example, if we have our $float plus 7, we'll echo that back Let's put some br tags here just so they get them each on new lines, and we can also divide two integers together in order to get floating point numbers. So 4 divided by 3 doesn't divide evenly, so as a result we end up with a floating point number. Let's try those out. So I'll switch back over to browser and we'll go to floats, so there we go, you see that it echoes the first value, 3.14, it adds seven, an integer to it, and gives you a result which is also a floating point number.

Doesn't matter that we have two different types, it handles them, they're both numeric, and so it knows that they can be added together. And the result might be an integer or the result might be a float. One important point that I want to make for you, is just that we can't divide by zero. Just be aware of that. It does not give us any kind of a floating point number or anything. It's an illegal operation, and we'll get a warning if we try and divide four by zero. Let's just try that real quick so you can see. Comes up and it gives us a warning, says oops, there's a warning, can't divide by zero. Once we learn how to do conditional statements, we'll be able to check and see, and have one behavior if something is zero.

And another behavior if it turns out not to be zero. There are some functions that we can look at with floats that are specific to floats, and that is basically regarding rounding. What do we do about rounding them to a certain number? Round, the function round takes a number that says how many significant digits do you want there to be? So, float, 1 will take my float number at the top, 3.14. And round it to one decimal place. Ceiling and floor are also a kind of rounding. Except that ceiling always rounds up, and floor always round down.

It doesn't follow the normal rules of rounding. Notice that ceiling is actually ceil, that that's the name of the function name, ceil And Floor is the other one. Let's try both of those out. Save that document, switch back to Firefox and reload, and you can see that it rounded 3.14 to be just 3.1. It rounded it up to 4 when I used Ceiling, and it rounded it down to 3 when I used Floor. Those are handy tools to have, especially when something doesn't divide evenly you can decide whether you want to round up or round down With the result.

Now with both integers and floating point numbers, we're able to ask PHP whether or not something is an integer or whether it is a float. We can do that like this. So for example, I can have PHP, we'll set integer equal to just 3. And then I'll just paste in a bit of code down here. And it says now, is integer. An integer is float an integer and then I'm going to use this method over here, which is, is underscore int to tell me true or false, is it an integer or not? We can do the same thing for float. Is it a float? And the method there is of course, is underscore float.

So it will return true false for each one of these is an integer or a float. And there's one more, which is we can use numeric on both of them, and we'll see what that gives us. Numeric is numeric. Alright, now notice that this is is_int, is_integer also works, that's an alias for it but is int is much more common, that's the one you'll see most people using. Let's try those out, we'll go over to firefox, and we'll reload the page. Is three an integer? Yes, it responded with true and true when it gets output as a string gets converted into a one. That's something we'll talk about when we talk about true and false later on. Is 3.14 an integer? No, it's false so it gets converted to nothing.

So that we see no result there. Is three afloat? No, it's not. Is 3.1 afloat? Yes, it is both of them though, are considered numeric. They both belong to this larger type, of being numeric. So this gives us the tools to be able to know whether something is afloat, whether it's an integer. Or even just when it's a number, regardless of which one of the two types it is. These kinds of tests can come in handy. Now that we understand how both integers and floating point numbers work in PHP let's take a look at another type, which is arrays.

Find answers to the most frequently asked questions about PHP with MySQL Essential Training.


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Q: This course was revised on 6/4/2013. What changed?
A: The old version of this course was 6 years old and it was time for a complete revision, using PHP 5.4. (The tutorials will work with any version of PHP and covers any differences you might encounter). The author has also added updated installation instructions for Mac OS X Mountain Lion and Windows 8. The topics and end project are the same, but the code is slightly different. It also addresses frequently asked questions from the previous version.
 
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