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Numbers part one: Integers

From: PHP with MySQL Essential Training

Video: Numbers part one: Integers

Over the course of the next two movies, we're going to be talking about numbers. And we're going to start out by first talking about Integers. Integers are whole numbers, so that's numbers like 1, 2, 3, 4, 5, as well as negative 1, negative 2, negative 3, and so on. I think what a number is, is pretty intuitive. We all kind of have an idea of that by now. But we do still need to see how we work with them in PHP. Let's create a new document we can work with. I'm going to open up basic.HTML and I'm going to do just Save As. I'm going to change this one to be integers.PHP. Make sure you've got PHP at the end. Integers.

Numbers part one: Integers

Over the course of the next two movies, we're going to be talking about numbers. And we're going to start out by first talking about Integers. Integers are whole numbers, so that's numbers like 1, 2, 3, 4, 5, as well as negative 1, negative 2, negative 3, and so on. I think what a number is, is pretty intuitive. We all kind of have an idea of that by now. But we do still need to see how we work with them in PHP. Let's create a new document we can work with. I'm going to open up basic.HTML and I'm going to do just Save As. I'm going to change this one to be integers.PHP. Make sure you've got PHP at the end. Integers.

Now, we've seen how we could just have our basic PHP tags and assign a variable. var1 equals 3, and var2 equals 4. And we saw how we can add those together and we can echo back the result. Let me go ahead and just show you a bit more math. We're going to be echoing the result back from adding 1 plus 2 plus the value of var1. That's 3, and then multiplying that by var2. This asterisk is what we use for multiplying when we're programming. And then, the result of all of that in parentheses is going to be divided by, that's what the forward slash here means, divided by 2 minus 5.

Now, the parentheses, the order of operations between the multiplication and division and all that, it's going to still apply. It's just basic math that follows the basic math rules. So, let's try that out. Let's open that up in a browser. Instead of string functions, we're going to be looking for integers. And there it is, basic math, the answer is 7. So, it added all of those together and did a calculation for us. Let me show you a few other math things that we can do, and that's to use some functions. So, here's if you want to find absolute value, you use the abs function.

So, 0 minus 300, that will, of course, return the absolute value, which would be 300 instead of negative 300. Exponential, raising something to the power of something. The function we're going to use is pow. So, you see the arguments are 2 and 8, so that's 2 to the 8th power, and then we have the square root, sqrt. The square root of 100, and then fmod is for modulo. Now, if you've never worked for modulo before, what it's going to do is it's going to take 20 and divide it by 7. And return just the remainder to me. What's left over from that, things don't divide evenly, it will tell us. That can be very handy for finding out whether one number divides evenly into another number.

And then rand, of course, will return a random number to us. And rand with a minimum and maximum value will return a random number within that range. Let's try all of those out. Save it. Back, and here you go. And you can see the random number it gave me was a really large number. Whereas the random min max it gave me was between 1 and 10. If we reload that page, you'll see that it gives me different values for each of those this time around. And you can see what I was also talking about with modulo. We were dividing 20 by 7, 20 by 7, will divide into it twice, with 6 left over.

So, the modulo is the remainder that's left after that. So, we could know that it does not divide evenly. In addition to these functions, I want to also show you how to increment and decrement the numbers a little bit. Let's do a new row here and let's, first, I want to show you how to do plus equals. So, we'll do some PHP, and we're going to say var2 plus equals 4. Now, what that's going to do is it's going to update variable 2 in place by adding 4 to it. It's the same way we were doing that concatenation in assignment at the same time when we were working with strings. And if the exact same thing as if we had actually typed out var2 equals var2 plus 4, it just saves us some typing to write it this way. Let's echo that value back just so we can see what it is, var2, we'll put a br tag at the end.

Now, not only is there the plus version of this, but there's a minus version, a multiplication version and a division version. So ,we can do all of those as well. And just so they aren't all exactly the same, I'm going to change this four to a three. So, that'll multiply it by 3 and then divide it by 4. Let's try this out real quick. Save the document. Switch back. We'll reload the page. And you can see they took the last value. It starts out with a value of four It adds four to it to get 8, which subtracts four to get 4. Multiplies by 3 to get 12, and then divides by 4 to get 3.

Now, incrementing and decrementing by one is super common, especially when we start working with loops. I'll just show you how that works, so we're going to call this increments. And if we want to increment plus equals 1, we could just do it like that. There is nothing wrong with that and it might actually be very clear what we're doing. But it's so common that we could just do it as var2++. That just mean adds one to it. Increment it. This actually comes from the world of C. C uses this when we're incrementing loops.

It's just a nice handy short cut. We can do the same thing with decrementing with minus, minus. So, if you're going through a loop and you want to keep a variable incremented. Every time you go through the loop to count your iterations through the loop, you can do that by using this plus, plus or minus, minus. And we could try it out real quick. As you would expect, it comes up and tells us that it went from 3 to 4 and 4 back down to 3. The last thing that I want to show you about integers before we move on to floating point numbers. Is I just want to make sure that it's clear to you that there is a difference between the number 1 and the string 1, right? Those are not the same thing. This is just a character.

It could might as well be x or y or z. It's just a character on the screen, it's not a number that's ready to be added. Now, in truth, PHP will do its best job to add it together. If we did something like this, PHP will say, all right, I realize this is not a number. So, it's not suitable for adding, but I wonder if I can convert it. I wonder if I can change it into an integer so that I can complete the operation. And it will do that. Let's just see that real quick, and you see it came up with two. But if I said this is 1 plus 2 houses, usually it comes up with 3. The word houses just disappears because it converts it. And the best way it can convert it to an integer is to pick the number that it see out of it.

And throw the rest of it away. And that's the only way that it knows how to. In general, you should not rely on PHP to convert strings into integers for you. You should be working with one or the other, and you should intentionally switch from one to the other if you really need to. And we'll talk about how to do that later on. But, it's considered sloppy programming to combine types like this without explicitly converting them to the right type.

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This video is part of

Image for PHP with MySQL Essential Training
PHP with MySQL Essential Training

131 video lessons · 35954 viewers

Kevin Skoglund
Author

 
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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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