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Variables PHP in MySQL

In PHP, an important structure is the use of variables in the code. Variables are used to represent … Show More

PHP with MySQL Essential Training

with Kevin Skoglund

Video: Variables PHP in MySQL

In PHP, an important structure is the use of variables in the code. Variables are used to represent values symbolically. The value of a variable is not fixed and may change over time. While coding in PHP there are some procedures for naming variables that must be followed. Learn about using and naming variables in this PHP with MySQL online tutorial.
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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. 1h 3m
    1. Overview
      2m 33s
    2. Working with Apache Web Server
      6m 56s
    3. Changing the document root
      7m 24s
    4. Installing to Yosemite
      8m 13s
    5. Enabling PHP
      6m 16s
    6. Upgrading PHP
      3m 30s
    7. Configuring PHP
      10m 3s
    8. Installing MySQL
      5m 46s
    9. Configuring MySQL
      7m 24s
    10. 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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Video Duration: 7m 50s 14h 24m Beginner Updated May 20, 2015


In PHP, an important structure is the use of variables in the code. Variables are used to represent values symbolically. The value of a variable is not fixed and may change over time. While coding in PHP there are some procedures for naming variables that must be followed. Learn about using and naming variables in this PHP with MySQL online tutorial.

View Course Description

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


Our exploration in the PHP programming language is going to begin with an exploration of the different structures or types that we can use while writing PHP. And the first of those that we're going to look at are variables. Now, if you've done programming before, then you're familiar with what a variable is. But if you haven't, then let me start by explaining that a variable is a symbolic representation of a value. You can think of it as a symbol that refers to something and that's going to make a lot more sense once we actually start using them. But as it's name suggests, it can change over time or vary. It has a variable value because it can point to different values. Now, in PHP, there's some rules about the kinds of names that we can give to variables.

They need to start with a dollar sign, that needs to be followed by either letter or an underscore, they can contain letters, numbers, underscores or dashes. They cannot contain any spaces and they are case sensitive. It makes a difference whether we use an upper case letter or a lowercase letter. So let me give you some examples of some variable names and then we can talk about them. So I could have item, which is just $item, and that could be a symbol that then points to an item. So maybe it's just number five, right? Item points to number five. I could also have Item with an uppercase I.

Either one is perfectly fine, but they are different. If I have two of them, if I'm using both of them, and I have item lower case pointing to the number 3, and Item upper case pointing to the number 5. Then depending on whether I use upper case or lower case will determine which one I get back. So you want to make sure that you're consistent with your capitalization. We can also have myVariable with a capital V. That is often referred to as camelCase, because those upper case letters in the middle are like the humps in a camel. So, some developers like that format. Then there's the underscore between words, so this_variable. There's also a dash, this-variable.

That's perfectly valid. You can put numbers in it. So product3, that's perfectly valid to have a third product named that way. You can put underscores in front of it. Remember, the first character has to either be a letter or an underscore, so you could have _book. You could even have multiple underscores, $__bookPage. Now, all of these are valid. Any of these will absolutely work. But I want to steer you towards some and away from others. The first one is I think we should not use the hyphenated version of this, and the main reason why is that, that hyphen looks like a minus sign, and it looks like we're subtracting this minus variable.

And when we start working with variables and we start working with addition and subtraction, that could be confusing for us. So let's avoid confusion and stay away from that. The second one is this multiple underscores. Stay away from that as well, because it makes it hard to tell whether you've got one or two underscores. I once worked on a project where another programmer had written their variable names using underscores. And sometimes they had one underscore, sometimes they had two, sometimes they had three, and it had significance to them. There was a reason why they were using one, two, or three, but it was really kind of lost on me as to what the meaning was behind these, and it was hard to read to tell whether it was one or two or three.

The last one is not quite as evil, but I want to steer you away from it and that is this single underscore at the beginning. The reason it's not evil is that PHP is going to use it itself. And we're going to see that. We're going to see that PHP has some special variables. They're named with this underscore at the beginning, and some developers use this underscore for special cases. They want to denote the fact that a variable has certain access privileges, that certain people can or can't access things by putting that underscore in front of it. Because it has this special meaning both to PHP and to other developers. Let's stay away from it for general use.

Let's go with the other ones. , ow the one that I'm going to use most often and the one that I prefer is the fourth one in this list, this_variable. And that's what you're going to see me using throughout this title. But you can use whichever one you feel most comfortable with. Now, you can't just use any single name that you want. PHP actually has some words that are reserved, words that you're not allowed to use for different things, and it's a good idea to take a review of this list, and then stay away from those words as much as possible. Sometimes, it's not a problem to use it for a variable name, but it might be a problem to use it in other contexts. It's basically just names with special meaning to PHP that we don't want to use. Now, let's try using some variables.

Before we do that though, let's open up our site's folder. Let's get all the way inside that site's folder and let's create a new directory inside here. So File > New Folder, and I'm going to call this sandbox. I find that it's very helpful to have a sandbox where we can put all of our miscellaneous files, like the ones that we've been working with here. So I'm going to grab basic.html, helloworld, my_phpinfo. I'm going to put all of those inside my sandbox. This index value, HTML file, I don't actually need anymore, and I can just throw that away. So, all of my files now are inside my sandbox and this is going to be a little place where I can try experiments out, certainly, while I'm learning PHP. But even after I'm actually developing, I can just jump back to my sandbox, try some things out, see if things work the way I expect, and then switch back to my application to apply what I learned.

I do this all the time. So it's really helpful to have this kind of PHP Sandbox. Let's now open up our basic.html file, and let's just do a Save As on that. And let's save that in our sandbox, as variables.php. Just make sure that ended up in our sandbox. You see there it is. And notice that it ends in .php. So now, we're ready to put in some PHP code. Just give myself a little room here and we'll change the name to variables. Okay, so we're ready to write some variables inside our PHP code and to start out with, let's just do a simple assignment, variable1.

That's the name of our variable, var1 and then we're just going to say it's equal to the number 10. That's it. We've now made that symbolic pointing from the variable to the number 10. Variable 1 now points to 10, and if we talk about variable 1, we're talking about 10. So if we then, in the next line say echo var1, it's going to echo back 10, right? Let's save it and just try it. Go back to Firefox, and instead of HelloWorld, now, we want, variables.

Nope, I forgot I have to put sandbox in front of that, because I've now moved everything to the sandbox. There we are. So there's the number 10. See how that works? It didn't output the actual string, var1. var1 is a variable that points to 10, and of course, this value can vary. We're just going to take these two lines, and let's paste it. And now, let's say it's equal to 100, right? Let's Save it, and before I output it, I'm just going to also echo a br tag in between them. I can echo HTML just like I can anything else and it will output that br tag in between the two of those.

Let's try reloading the page. Now, we got 10 and 100, so var1 the first time points to 1 thing. The second time it points to something else, because I changed its value. It varied. Notice, also, that it's case sensitive. If I had said that this was equal to, I was going to echo back var 1 with a capital V. I save it. It comes up and it says oops, we have a problem here, I don't see that Var1 with a capital V has been initialized, and I get a warning message. This is what a notice looks like in PHP. So var1 here is different from Var1 with a capital V there.

Now, variables don't only point to number, they can point to other things as well. Also, for example, we could have var2 is going to be equal to hello world. And then echo var2. Save that. Come back here, reload the page, and you can see that now the outputs Hello world. So variables can point to anything really. It's just a symbolic representation of something larger, and it gives you a sort of handle, an easy way to work with this larger thing.

And just refer to it by this symbolic name. We'll continue working with variables and text like Hello world in the next movie, when we talk about the data type called Strings .

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.
Q: This course was updated on 5/20/2015. What changed?
A: We added one movie called "Changing the document root in Yosemite," which helps the Mac installation run more smoothly.





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