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PHP with MySQL Essential Training

Encoding GET values


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PHP with MySQL Essential Training

with Kevin Skoglund

Video: Encoding GET values

Now that we know how to construct URLs to be used as links, we need to talk about the characters that we're allowed to use in those URLs. URLs can contain the most common characters like letters, numbers, underscores, and dashes. But there are some characters that are going to cause problems because they have special meaning to the URL. These are known as reserved characters. Here are a list of the reserved characters that we have problems with if we include them in the URL. You can see there are quite a few. When we're constructing URLs for lengths, we must encode these characters so they don't interfere with the function of the URL.
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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

Encoding GET values

Now that we know how to construct URLs to be used as links, we need to talk about the characters that we're allowed to use in those URLs. URLs can contain the most common characters like letters, numbers, underscores, and dashes. But there are some characters that are going to cause problems because they have special meaning to the URL. These are known as reserved characters. Here are a list of the reserved characters that we have problems with if we include them in the URL. You can see there are quite a few. When we're constructing URLs for lengths, we must encode these characters so they don't interfere with the function of the URL.

Encoding a reserved character means converting that character to a percent sign followed by a pair of hexadecimal digits. Hexadecimal just means that in addition to zero to nine, we can use the letters A through F as if they were digits, too. So, what we'll need to do is be able to convert each of these characters into its hexadecimal form, put it in a URL. And then we'll decode it by converting it back once the page is received. PHP lets us perform the URL encoding by using a function called urlencode, and its argument is the string that you want to encode.

So, urlencode is going to take letters, number, underscores and dashes and let them pass through completely unchanged. But those reserve characters, that we just saw, are going to become their hexadecimal equivalent. That percent sign, follow by two digit hexadecimal digit number. And spaces are going to become plus signs. Remember that, because that's going to be important in a minute. We'll talk about that. Let's try using it. So, let's go back to our first page. In addition to sending ID 5, let's also add another one here. Let's do an &company equals and we'll put a company name. We'll put PHP echo $company, there we go.

And then, up here, we're going to provide that company name. $company equals and that company name could be any string. So let's imagine that we're looking at a directory of employees lets say. And we're going to look at a company called Johnson & Johnson. Do you see the problem here? It has an ampersand in it. So, let's just try it on its own. Let's save it. Let's go back to first page so that we can see what the problem is, I'm just going to go first page.php. Alright. It generates the link just fine, but when I click on it gives me a hint what it's going to do down at the bottom. When I click on it you'll see up here that the URL is Johnson space and space Johnson.

Let's go over to our second page, and let's echo that value. So, I'm just going to copy this, for now. Paste it, and we'll just change it to company, and company, and company. So, it's going to get that company value out of it. So, reload the page, Look what I got, Johnson. That's the company, because it saw this ampersand, and it said, oh, that's a new query parameter. That's what's used to divide those. So, you see what the problem is now. Now, the solution is to use urlencode. So, what we do is we provide urlencode right here, urlencode, this string.

Make sure that you use echo with urlencode, super important. This will not do it for you. This will encode it, but then it'll throw the value away. Nothing will happen with it. You need that echo there. So, make sure you've got that. Echo, the urlencoded value of company. Let's save it. We'll hit the back button. Go back to first page, I'll just reload that page. Now when I click on it, now look what it gives me up here. Johnson a plus sign for the space, and then the ampersand became % 26. And then when I pulled the value back, it correctly found it. It correctly changed the ampersand back, converted those spaces back as well. Now, we didn't actually do any decoding.

It's because PHP automatically does the decoding for us when it assigns those values to the get superglobal. It's kind of assumed the values are encoded and ready to be used. In which case they need to be decoded so that we can use them. So, it just does it automatically for us. We don't actually have to decode. There is a function called urldecode that works exactly like you would expect that you can use if you ever need it. Must most times you don't need to. Now I just want to insert a little parenthetical here that this is just for get requests only.

Later when we start working with posting cookie, we won't need to do this encoding. This is just forget request because those values are in the URL string at the top. So we're URL encoding them. So, now that we know about URL encoding, there's another type of encoding that we need to talk about called raw URL encoding and it's important to understand and to know the differences. So, if we take a look at what we had for urlencode, we saw that letters, numbers, underscores, and dashes are unchanged. It converts the reserved characters and spaces become plus. With rawurlencode, just put the word raw in front of it, no spaces or underscores, just all smashed together, letters, numbers, underscore and dash are unchanged.

The reserved characters get converted but, here's the big difference. Spaces become percent 20. They get encoded into a two-digit hexadecimal also instead of using the plus. It may seem like a minor point, but it does make some big differences. It's easy for us to try it. We'll just pop back over here, and we'll just type raw in front of urlencode. Now we'll come back here. We'll go back to first page, we'll reload the page. And you can see now, when I click on it, now it is Johnson space Johnson with the percent 26 encoded. So, now you may be thinking well wait a minute, I thought you told me that it was going to convert this space into percent 20.

It actually did. Let's go back real quick to the first page and let's view. Page source, here we go. See, here they are. Percent 20, percent 26, percent 20. That's what the link was on this page. Then when I clicked it, and it shows up in the URL. Firefox is helpfully converting those back to spaces for me. But not all browsers do that. It is percent 20. That's what you're actually sending. So, now that we understand the difference. One send pluses, one sends percent 20. You're probably wondering, when should you use each one? Well, here's my guideline for you.

You're going to want to use rawurlencode on the path, that's the portion that comes before the question mark. So, everything comes before that, if there's anything dynamic in there that you're generating, like the page name. That is all going to be done with raw URL encoding, because the spaces must be encoded as %20 for the final system to be able to find that file. For Apache to be able to locate the PHP page you're looking for, it needs it as %20. But, you want to use urlencode on the query string. That's everything that comes after question mark.

That's because spaces are better encoded as plus. Now it worked fine as you saw when we used percent 20 and used rawurlencode on it, but the plus sign is going to be a better more compatible way to do it. However, rawurlencode is more compatible generally. So, if you ever have a doubt, if you're working with JavaScript let's say, you're doing an Ajax request, something like that. You're working with communicating with another server via an API, rawurlencode is probably what you want. Urlencode is an early standard for how webservers should work. Rawurlencode is based on a subsequent standard that came later. So, it's the newer and later version and most times it's going to be better. However, when we are working with URLs rawurlencode the path, urlenconde the query string.

Let's make ourselves a quick page that can demonstrate this. I'm going to come back over here, and I'm just going to take first page, and I'll do a quick Save As on it. I'm going to call it urlencode.php, and let's call it urlencode. We'll make it this way. And here in the body I'm just going to paste in an example. And I've got a page that's going to be used as a bio, so I'm looking for bio for William Shakespeare with a space in it. I'm going to rawurlencode that and then I'm going to ask for a quote that's going to be the parameter I'm going to send of to be or not to be. And I'm going to urlencode that.

Let's just bring that up and take a look at it real quick. So, make sure that you save it. And then, let's do urlencode. And there you go. See the percent 20 there, versus to be or not to be. This, the file system will be able to find for you. If we, instead, flip those around. Make link two. And let's just swap these. Let's make this one raw. And this one is not raw. And then we'll just echo back like two for contrast. Now the file system is going t be looking for something called William plus Shakespeare.

A literal plus sign not a space. So, that's not going to find the file to begin with. And then this to be or not to be. Probably will work out for us okay. Usually, most web servers and PHP can sort that out. But this is the better way to do it. This is going to look better, it's going to work better all around. Rawurlencode, everything that's on this side of the question mark, urlencode everything that comes after it.

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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