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Binding output variables

From: Accessing Databases with Object-Oriented PHP

Video: Binding output variables

We've created a prepared statement that uses placeholders to and it's our statement object and the bind_result method that we need.

Binding output variables

We've created a prepared statement that uses placeholders to insert values from an online form into an SQL query. To make it easier to handle the result set, we can bind the results of each column to named variables. So, instead of using the get_result method on line 17, we're going to use the bind_result method which takes as its arguments, the variables you want to bind the results of each column to. So, we'll get rid of this and it's our statement object and the bind_result method that we need.

The number of arguments passed the bind_result must be exactly the same as the number of columns in the result set. And they must be in the same order. So you should always declare the column name specifically in the SQL when binding the result. So, let's see. We need one for make, yearmade, mileage, price, and description. They have to be in that order. We've already got a variable called make, so we'll bind the output to maker. Then year, miles, price, and desc.

price, and desc. So, after binding the output like this, we need to make a few more changes to the rest of the script. So, scroll down. And the first change needs to be made here on line 64. The original code was using a mysqli result object. And this has got a num_rows property. We're no longer using that result object, but the statement also has a num_rows property, so we can change that from result to statement, and then further down, originally we were using the result object to fetch each row into an associative array.

we were using the result object to fetch each row into an associative array. That's no longer necessary. So let's change that. And what we need to have is the statement object. And that calls, not fetch_assoc, but simply fetch. And we can now change these variables down here to the variables that we created just a moment ago. So, instead of row make, it becomes maker, and instead of row yearmade, we use year.

Row mileage becomes miles. Row price is price and then row description is simply desc. So, we can save that and test it in a browser. Let's search for some cars that we know are definitely there, I know there are Ford in this table, so let's search for that. And we've got no results found. So, what's gone wrong? Well, by default, prepared statements return unbuffered results, and the problem lies with the number of rows that are being reported.

Lets go back to the code. And up here on line 64. We're accessing the statements num rows property, but because it's unbuffered, it doesn't know how many rows there are. So, what we need to do is to store the result first. So, we call the statement object's store_result method. Save and go back to the browser. Search for ford again. And this time, we get the results that we expected. So, it's important to know that if you're trying to find out the number of results from a prepared statement, you must store the result before you can access the num_rows property.

result before you can access the num_rows property. So, let's just review what we have done. Instead of getting the result directly, and storing it in a mysqli result object, we use the bind_result method on the prepared statement object. That requires as its arguments the variables which you want to bind the results of each column to, and the number of arguments passed to bind_result must be exactly the same as the number of columns in the result set and they must be in the same order.

And if you want to find the number of rows in your result, you need to store the result first using the store_result method, before you can access the num_rows property of the statement. And then, you use the statement's fetch method to fetch the results. Binding the results of a prepared statement to output variables is particularly useful when you've got a lot of columns and you want to embed the values into double quoted strings. It's a lot easier than working all the time with an associative of indexed array.

In this example, the prepared statement has been used only with a select query, but prepared statements can be used with any other type of query including insert, update, and delete.

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This video is part of

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Accessing Databases with Object-Oriented PHP

47 video lessons · 2731 viewers

David Powers
Author

 
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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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