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PHP with MySQL Essential Training
Illustration by Don Barnett

String functions


From:

PHP with MySQL Essential Training

with Kevin Skoglund

Video: String functions

We've seen the basics of working with strings. Now I want us to take a look at some functions that we can use with strings. We haven't looked at a lot of functions yet. So far we've really just looked at the PHP info function and Echo. Those are really the two main functions that we've seen. So we're going to start diving into the world of functions. And before we do, I just want to remind you that the php.net website has some excellent documentation for functions. And it will tell you all of the different functions that are predefined in PHP, it'll tell you how to use them, has good user submitted tips for you, all of that's there. And you can browse through those if you're looking for something, you're not quite sure what it is. Or if you know the name of the function you can just type it into the search bar at the top and it will return the documentation for it directly. Alright.
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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

String functions

We've seen the basics of working with strings. Now I want us to take a look at some functions that we can use with strings. We haven't looked at a lot of functions yet. So far we've really just looked at the PHP info function and Echo. Those are really the two main functions that we've seen. So we're going to start diving into the world of functions. And before we do, I just want to remind you that the php.net website has some excellent documentation for functions. And it will tell you all of the different functions that are predefined in PHP, it'll tell you how to use them, has good user submitted tips for you, all of that's there. And you can browse through those if you're looking for something, you're not quite sure what it is. Or if you know the name of the function you can just type it into the search bar at the top and it will return the documentation for it directly. Alright.

Let's take a look at a few. So lets start by opening up our strings.php that we were just working on before. And we'll just do save as on that real quick. And make this string_functions.php. That's what we're going to call it string function and lets take everything out between all these PHP tags here. There we go. Now I have a nice space to to drop in my code. I'm going to start by just pasting in some text, so you don't have to watch me create it. You can pause the movie if you want to copy some of this down. I've got a string that I'm assigning to the variable first. The string is, The quick brown fox.

And I've got another string, jumped over the lazy dog with a space at the beginning, that I'm assigning to second. So we've seen how we assigned variables to strings, like we're doing there. And we've also seen concatenation. We've seen how we can just concatenate these before. I want to show you another way to do concatenation real quick. We're going to do concatenation and assignment at the same time. So let's say we have third, it's going to be another variable. And third is going to be equal to first. And then, on a new line it's going to be third is equal to concatenated equal to second.

Alright, do you see what it's doing there? So it says, alright, first of all third points to the same thing as first does. You're going to get that same string and bring it into third. Now in the next slide, I'm going to tell third that it should add on the second string to the end, because you can concatenate it to what's already there. It's like appending it to the end. The values of first and second haven't changed. Those values are exactly the same still. But third now has the complete phrase in it. This is going to be a very handy way to write your code if you're trying to build up a string over time. We'll definitely use it when we start working with MySQL later on. And, of course, I could then say echo $third.

Alright. So now that we have our third string, let's take a look at some functions. I'm just going to drop down here a little bit. Let's put in a br tag and instead of opening PHP tags again I'm going to paste in more text here. This includes some HTML as well as PHP tags calling some functions. So these are the string functions that we're going to be learning. The first function that I want us to look at is stringtolower. So strtolower, that's the name of the function. And functions often take something as an argument.

They take something as input into the function, and then they return output to you. So the input in this case, is going to be inside the parentheses, and it's going to be our variable third, which is equal to The quick brown fox jumped over the lazy dog. So that whole phrase is being sent in to string to lower. And you can guess what string to lower does, it lower-cases it. So it then returns a lowercase value, and then, echo, another function, echoes it back. So we're calling one function, on the results of another function. The argument to echo is the results of string to lower.

Now we have the same thing here with string to upper, raising it to uppercase. ucfirst is going to make the first letter uppercase, and ucwords will make the words all uppercased. So let's just try that out, so we can see what it does. Let's save it. Let's go back to Firefox. And instead of strings, we're now going to be loading up string_functions. (SOUND) So there it is. So you see here's the original phrase that we echoed the first time. Here's the lower case version, the upper case, the upper case first only. Everything else stayed lower cased and upper case words for each one gets upper cased.

So, make sure that you understand that idea before we go on. Let's just do a few more here. I'll just put a br tag and we're going to do length string, len, strlen is going to tell us the length of the string. Trim, I'm going to use a different phrase here, just to illustrate it. What trim does is it removes the leading or trailing white space. Right? That's spaces. No matter how many there are, it gets removed. So I've got A being concatenated with a trimmed version of B C D, followed by E. Alright? So there should normally, if there was no trim here, it would be A space B space C space D space E.

But the trim is going to take out those spaces. We'll see that in a second. Find, which uses strstr. That's the function name. The way you can remember that is that you're finding a string within a string. That's why it's called strstr. So inside the string that $third points to, we're going to look for Brown. We'll see what that returns. And then replace by string is going to replace quick with super-fast inside third. So it takes three arguments, right? So we now have some that takes two arguments. Another one that takes three arguments. The order of those arguments is important and it's something that you have to look up or know already from the way the function works. And you can look those up on the PHP.net website if you forget them. The way that string replace works is it wants the thing you're looking for, the thing you're replacing it with, and then the item we're searching inside of. They call it the haystack often.

We're searching for a needle in a haystack, well the haystack is third and the needle we're looking for is quick. We're looking for quick inside third and we're going to replace it with super-fast. So let's try those real quick and see what those look like. Go back, just hit Reload. So the length of it is 45 characters long, that's how many letters and spaces there are in there. Notice here that the spaces got trimmed out of b c d, so that there is no space now between a b and d e. Find, did find the word brown. Notice what it returned to us. It returned everything after that in the string.

So, it found it and the result, what it returned back, was not just the word itself, it was everything that follows. That's the behavior of find. Again, the documentation will tell us that that's the way it behaves. And we might want to slightly modify that or account for that in our code to handle it, if we were looking for something like we want the word that follows brown, well we then have to apply a few more functions to it, so that we could get the word fox from that. Replace by string, you can see that it put the super-fast brown fox, so it did exactly what we would've expected.

Okay. Let's look at one last set, br. (SOUND) And we're going to look at repeating str underscore repeat, we'll repeat a string. It's going to repeat third two times, echo substring substr, that's going to make a substring from third, starting at the fifth position to the tenth position of the string. And string position is going to tell us the position of brown, tells us where brown is located. Or we can find a character, where is the character z located, it will return a number to us telling us where that's located.

These positions can be really helpful for trying to parse out, we're trying to find where something is and then make a substring from it. Then you can see how we can use a combination of tell me what the position is or find it for me and then make a substring starting at this position going until whatever position is, you know, at the ending position. Let's try those out real quick. Let's go back, and you see repeat, the quick brown fox jumped over the lazy dog, the quick brown fox jumped over the lazy dog, make substring, you can see where it grabbed, it grabbed from the fifth character going forward. Notice that the fifth character is 1, 2, 3, 4, 5, right? So that's where it started from the UIC.

And then, find position of brown as in the tenth position, and then find character. We were looking for z. It works the same way that find did, right? When we were up here, it found brown and returned everything after it, returning z returns everything from z going forward from there. So these are your first set of functions. This is the way that PHP is going to work. We're going to be able to manipulate all sorts of things by using different functions, and these are the string functions. These are not the only ones. There are a lot more and I don't expect that you will have memorized all of these.

You're going to be looking them up for a while, so they become second nature to you. You're going to have to make yourself some notes. Keep yourself a little chart, maybe jot down the ones, you know, that you use most often. So that there is a handy reference or just keep the PHP.net website open, so that you can quickly go and search and look up, how you use each of these. I've been using PHP a long time and I'm still constantly looking up, the usage of these and the order of the arguments and that kind of thing. Now we've explored strings and string functions. We're ready to move on and look at integers.

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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