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Introducing prepared statements

From: PHP with MySQL Essential Training

Video: Introducing prepared statements

Prepared statements are a feature of MySQL, and of many other databases. The topic is too advanced for an introductory tutorial, but I do think it's important for you to understand what they are. The general idea is that you give MySQL a template for a query that you want to run, with places indicated where you can fill in the blanks later. For example, we might have an insert statement, and in place of the three bits of data that we would be dropping into the columns, we would put question marks. Those are place holders for where the data is going to go later. Then when we want to run the query: we call up the template, fill in the blanks and then MySQL to run it. So why do it this way, why go that extra step? Well, because when any query runs, the database has to parse the query and develop a plan for running it. With prepared statements, the database will do this work once and then you can reuse it for future queries where only the variables change. The parsing and the plan of attack stay the same. This can be faster, especially if you're doing complex queries, repeating a query many times.

Introducing prepared statements

Prepared statements are a feature of MySQL, and of many other databases. The topic is too advanced for an introductory tutorial, but I do think it's important for you to understand what they are. The general idea is that you give MySQL a template for a query that you want to run, with places indicated where you can fill in the blanks later. For example, we might have an insert statement, and in place of the three bits of data that we would be dropping into the columns, we would put question marks. Those are place holders for where the data is going to go later. Then when we want to run the query: we call up the template, fill in the blanks and then MySQL to run it. So why do it this way, why go that extra step? Well, because when any query runs, the database has to parse the query and develop a plan for running it. With prepared statements, the database will do this work once and then you can reuse it for future queries where only the variables change. The parsing and the plan of attack stay the same. This can be faster, especially if you're doing complex queries, repeating a query many times.

But more importantly, prepared statements separate the query from the dynamic data. This completely, 100% eliminates the possibility of SQL injection. It even eliminates the need to escape your values to prevent it. Because the blanks where the data goes are so clearly defined, and the data that's going in there, is going to be cast into the right type. So the database will handle it for you, it'll make sure that it puts the right kind of data in the right spot, and it won't accidentally inject SQL. Now, as I said, we aren't going to be using these in this tutorial, but they have come into pretty common usage in PHP, so I think you should at least recognize them. Let's take a quick peek at an example before we move on. So, this would be an example of a prepared statement. You would open up your database connection, you would design your query, but then you would have question marks in place of username and password, where the data would be dropped in.

Those are the fill in the blank spots. Then you would call mysqli_prepare to prepare the statement, and then from on we have a statement object we can work with. The magic of this happens with the bind_param function. so, mysqli_stmt_bind_param takes variable values and drops them into those spots and that's where the escaping takes place. After that we tell it to execute the statement. We get back the results, we have to do a little bit of extra work with those, but in the end we can work with that data the same way that we normally do. Now, there are a few quirks with prepared statements that make them a little bit harder to pick up, until you've had more experience with PHP.

So for now, you should stick with what we've learned and query the database the standard way and escape your values using mysql real escape string. At least now you know what lies ahead for you when you do start working with prepared statements. (BLANK_AUDIO)

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PHP with MySQL Essential Training

131 video lessons · 33120 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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