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Freeing resources that are no longer needed

From: Accessing Databases with Object-Oriented PHP

Video: Freeing resources that are no longer needed

{QTtext}{width:960}{textColor:65280,65280,65280}{justify:center}{timescale:1000}{backColor:0,0,0}{plain}{font:Verdana}{size:20} Most of the time, PHP automatically frees With a prepared statement calling the With the MySQLi result object, all three have the same meaning.

Freeing resources that are no longer needed

Most of the time, PHP automatically frees up memory when resources are no longer needed. So it's common practice to leave the job of freeing resources to PHP's garbage collection. But with MySQLi there are times when you need to free resources explicitly, and in fact it's recommended you always do so. There are three methods that free up database resources in MySQLi, close, free and free_result. Let's take a look how they're used.

With a prepared statement calling the With the MySQLi result object, all three have the same meaning. close method, destroys the statement object, They free the memory associated with the result set and destroy the result object. and cancels any results that haven't yet been retrieved from the database. Because prepared statements aren't buffered by default, you need to call the Close method before attempting to submit another query if the result set hasn't been completely consumed. Alternatively, use the store _result method to buffer the result set. Calling the free_result method frees up the memory associated with a result set that's been buffered using store_result.

Alternatively, use the store _result method to buffer the result set. Calling the free_result method frees up the memory associated Unlike close, it doesn't destroy the statement object, so you with a result set that's been buffered using store_result. can use it to prepare and execute another prepared statement. Those close method also closes a database connection. That's how the close, free, and free result methods are used, but do you really need to bother? The one situation where it's vital to free resources is to avoid the commands out of sync error.

is to avoid the commands out of sync error. This happens when you have unused results in an unbuffered query and want to issue another query. You need to free the resources associated with the unused results. Alternatively, you must store any unbuffered results before issuing further queries. In all other circumstances, PHP automatically closes resources when the script ends.

closes resources when the script ends. Nevertheless, the recommended best practice is to close MySQLi resources as soon as they're no longer needed. With short example scripts such as in this course, it makes little or no difference. But on a busy website, freeing memory and handing back control to the MySQLi server could improve efficiency. It's also a good idea to free the memory associated with multiple result sets as soon as they're no longer required.

with multiple result sets as soon as they're no longer required.

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Accessing Databases with Object-Oriented PHP

47 video lessons · 1922 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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