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Returning values from a function

From: PHP with MySQL Essential Training

Video: Returning values from a function

All of our functions, so far, have been using echo to send output to the user's screen. But more often than not, we don't want that behavior. Usually, we'd like to get a result back from the function, and then decide what to do with that result ourselves. We might end up deciding to echo it to the screen, but we might instead take that value and continue to use it to do more processing. If it outputs from inside the function, then we lose that flexibility. It's better to get back a value. And for that, we need to understand, how to return values from a function. Let's open up basic.html, and we're going to do Save As on this.

Returning values from a function

All of our functions, so far, have been using echo to send output to the user's screen. But more often than not, we don't want that behavior. Usually, we'd like to get a result back from the function, and then decide what to do with that result ourselves. We might end up deciding to echo it to the screen, but we might instead take that value and continue to use it to do more processing. If it outputs from inside the function, then we lose that flexibility. It's better to get back a value. And for that, we need to understand, how to return values from a function. Let's open up basic.html, and we're going to do Save As on this.

We're going to call this one functions_returnvalues.php. (SOUND) Functions: Return Values. So let's just write a simple function here. I've got an add function. It takes two arguments value 1 and value 2. It adds them together and assigns them to sum. So let's just load this up in Firefox to begin with. Let's bring this up. And instead of functions arguments, instead now we're going to be loading up return values with no space in between.

Alright, I get nothing back. You can see it did load the page, but all I did was define the function. I haven't actually called it yet, so let's try calling it now. Add 3,4. All right, let's save that. Let's go back and reload the page. Still didn't get anything back. Why not? Well, it's because we're not echoing anything from inside the function like we did before. We could put an echo here, echo $sum and that would now output a value, but that's not as flexible. That doesn't return the addition to us so work with it.

The only option it gives us, the only way to get a value out is to print it to the browser. Now we could try printing this value from outside the function. Let's try that. Lets do after we add them together, let's echo that value. And it comes up and says nope undefined variable, because sum is a variable that's only inside the function. It doesn't exist outside the function. So we can't use this as a way to get values out of there. Instead, what we want to do is we want to return a value from the function. So we would have return and then what we want it to return, sum. So now it'll return sum to us.

And then, we need to catch that result here by saying the result is equal to Add 3 and 4. Now, we get back the result and we have the ability to echo that result to the screen. Let's take a look at that. And now we get the value of 7. Now, we don't have to echo this to the screen. We could, instead, do more operations with it, right? We could have, now the result is to take 5 and add that to result, what result was previously.

I can actually name these results 1 and 2 if that makes it a little clearer instead of overriding the other one. So result 2 know is equal to result 1 plus 5, come back here, and we get 12. Right. Much more flexible. We have the ability to output it or the ability to keep working with it... The best practice when you have functions is to always have a return value. Explicitly, say, what does this function return? Maybe what it returns is null. Maybe what it returns is the original input again. Maybe your, your input was an array, and so the output is to output that same array again.

But you always want to return something from your functions. The PHP functions have return values. All of those are listed on the PHP.net website. There's usually a section that say's the return values. It tells you what the inputs are and it tells you what the outputs are, so you can look those up. Now the return also exits the function immediately. It's similar to how a break works. Where break just got us out of a loop immediately, or out of a switch statement immediately. Well, return works the same way for functions. It says, alright, just stop whatever you're doing.

Let's exit the function and return this value. This is the thing that needs to be passed out of the function. No more processing required. And even if we put it inside loops or switch statements that are in the function, it will immediately exits from those as well. So, let's try an example here. Let's go back. We did the Chinese Zodiac before. Let's paste an example using that again. Should put a br tag here. I've defined the Chinese Zodiac as a function. So, here it is, Chinese Zodiac, we pass in a year. And then it takes that year and does the same processing we did before.

But now, instead of having assignment to a variable followed by break. Instead now, we're just going to return the value, that's it. So, case 0, return Rat. Done. No break required. And then, let's jump down here, and let's actually call our function. So let's say, $zodiac is going to be equal to chinese_zodiac. And let's put in 2013 as the year. And then after we've done that, we'll echo back a string, 2013 is the year of the, and put the zodiac here. I'll end it with a period.

And it'll be our tag. And a semicolon at the end. Alright, so let's bring that up and try it. There it is. See how that works? Now we have a function that (INAUDIBLE) wraps all of this logic for us. So now, whenever we want to call this, we can just simply call it with the new number. Let's say that we're looking for 2027, 2027 is the year of the, what? Goat. Now we don't have to assign this to a variable here. Sometimes it's cleaner to do it that way but I can do this in-line as well. We can't do it with the curly quotes but we can do it if we break those and use append and then we can just put it right there.

See how I've done that? Let me just widen my window a little bit. So I'm concatenating there. 2027 is the year of the, then call the function and then the br tags. Let's save it and go back and check that out. And there it is. It looks exactly the same. Now, by the way, I think it's a good practice to rarely have functions which output directly from inside the function. Now that's what we've been doing before now as examples because we didn't know how to do return values yet. But most times I think it's better to build up text inside the function and assign that to a variable. And then, return the value of that variable at the end. Then we can echo that returned value if we want, or we can do something else with it.

But it's better, I think, to leave echoes out of your function. So, for example, we could redo our hello function that we had before. (SOUND). Right? And we had better_hello. Instead of echoing from inside that function, just change it to a return. Return that result, and now, we can just as easily call echo better_hello, with Hello, and then, John Doe, followed by an exclamation point. Right? We can still call it that way but see how much more flexible this is.

We could take this and we could call up case on it or title case or something else before we output it. We have more flexibility. So I think it's better to leave echo statements out of your functions and instead use return values.

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This video is part of

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PHP with MySQL Essential Training

131 video lessons · 32866 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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