Accessing Databases with Object-Oriented PHP
Illustration by Don Barnett

Accessing Databases with Object-Oriented PHP

with David Powers

Video: Binding input and output values

Before diving into the details of PDO prepared statements, let's take a Prepared statements use placeholders for values that aren't known in advance BindValue can be used with a variable, as long as it's value is already set.
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  1. 13m 33s
    1. Welcome
      1m 4s
    2. What you should know before watching this course
      2m 8s
    3. Using the exercise files
      4m 56s
    4. Setting SQLite permissions
      1m 11s
    5. A quick primer on using PHP objects
      4m 14s
  2. 10m 12s
    1. Overview of PHP database APIs
      4m 5s
    2. Using prepared statements
      4m 24s
    3. Using transactions
      1m 43s
  3. 48m 57s
    1. Creating a database source name
      2m 3s
    2. Connecting to a database with PDO
      7m 27s
    3. Looping directly over a SELECT query
      3m 49s
    4. Fetching a result set
      8m 3s
    5. Finding the number of results from a SELECT query
      7m 14s
    6. Checking if a SELECT query contains results
      3m 32s
    7. Executing simple non-SELECT queries
      6m 2s
    8. Getting error messages
      7m 17s
    9. Using the quote() method to sanitize user input
      3m 30s
  4. 39m 51s
    1. Binding input and output values
      2m 36s
    2. Using named parameters
      9m 51s
    3. Using question marks as anonymous placeholders
      2m 35s
    4. Passing an array of values to the execute() method
      5m 20s
    5. Binding results to variables
      7m 53s
    6. Executing a transaction
      6m 54s
    7. Closing the cursor before running another query
      4m 42s
  5. 21m 20s
    1. Generating an array from a pair of columns
      2m 44s
    2. Setting an existing object's properties with a database result
      4m 42s
    3. Creating an instance of a specific class with a database result
      6m 1s
    4. Reusing a result set
      7m 53s
  6. 38m 14s
    1. Connecting to a database with MySQLi
      5m 57s
    2. Setting the character set
      1m 57s
    3. Submitting a SELECT query and getting the number of results
      4m 4s
    4. Fetching the result
      7m 35s
    5. Rewinding the result for reuse
      3m 20s
    6. Handling non-SELECT queries
      5m 27s
    7. Getting error messages
      5m 47s
    8. Sanitizing user input with real_escape_string()
      4m 7s
  7. 27m 49s
    1. Initializing and preparing a statement
      4m 17s
    2. Binding parameters and executing a prepared statement
      5m 55s
    3. Binding output variables
      5m 6s
    4. Executing a MySQLi transaction
      7m 5s
    5. Dealing with "commands out of sync" in prepared statements
      5m 26s
  8. 24m 7s
    1. Buffered and unbuffered queries
      4m 19s
    2. Using real_query()
      6m 1s
    3. Freeing resources that are no longer needed
      2m 31s
    4. Submitting multiple queries
      6m 41s
    5. Creating an instance of a class from a result set
      4m 35s
  9. 3m 31s
    1. PDO and MySQLi compared
      3m 31s

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Watch the Online Video Course Accessing Databases with Object-Oriented PHP
3h 47m Intermediate Jul 07, 2014

Viewers: in countries Watching now:

Now that PHP has true object-oriented capabilities, it's best practice to access databases using PDO (PHP Data Objects) and MySQLi. These methods produce database-neutral code that works with over a dozen systems, including MySQL, SQL Server, PostgreSQL, and SQLite. Learn how to use PDO and MySQLi to perform basic select, insert, update, and delete operations; improve security with prepared statements; and use transactions to execute multiple queries simultaneously. Author David Powers also covers advanced topics like instantiating custom objects, and compares PDO to MySQLi so you can decide which method is right for you.

Topics include:
  • Connecting to a database with PDO or MySQLi
  • Fetching a result set
  • Executing simple non-SELECT queries
  • Sanitizing user input
  • Binding input and output values
  • Passing an array of values to the execute() method
  • Working with advanced PDO fetch methods
  • Executing a MySQLi transaction
  • Freeing resources that are no longer needed
  • Submitting multiple queries
  • Creating an instance of a class from a result set
Subject:
Developer
Software:
PHP
Author:
David Powers

Binding input and output values

Before diving into the details of PDO prepared statements, let's take a quick look at the different methods for binding input and output values. Prepared statements use placeholders for values that aren't known in advance or that come from external sources such as an online form. All the examples in this chapter are select queries, but you can use placeholders in prepared statements for insert, update, and delete as well. You bind values to placeholders using the bindParam or bindValue methods.

I'll explain the difference in a moment. Alternatively, you can parse an array of values directly to the execute method. A prepared statement can also bind the output values of a result set to named variables using the find column method. This avoids the need to use an associative array, simplifying embedding the results in HTML. When binding input values to placeholders, bindParam and bindValue achieve the same result but there's a subtle and perhaps confusing difference.

bindParam works only with a variable, you can't pass it an expression such as a calculation or a string concatenated to a variable. This is because the value is evaluated Until the statement is executed. In other words, you're binding the variable rather than it's value. If you attempt to use bindParam with anything other than a variable, you'll get this cryptic fatal error message that you can't pass parameter two by reference.

The solution in such circumstances is to use bindValue, which binds the value immediately, so the value must be known. BindValue is also useful for setting a field to NULL. For example, this is how you would set a named parameter called ID to NULL. The first argument is a string containing the name parameter. The second is the NULL value and the third argument is a PDO constant for the NULL data type. BindValue can be used with a variable, as long as it's value is already set.

However, you should normally use bind value only when you need to use an actual value or to combine a variable with an expression such as a calculation or as part of a string. For a variable on its own, always use bindParam. For a complete list of the PDO Constants that can be used with bindParam and bindValue, see the PHP online documentation at this location.

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