PHP Unconference Europe 2015

mysql_free_result

(PHP 4, PHP 5)

mysql_free_resultFree result memory

Description

bool mysql_free_result ( resource $result )

mysql_free_result() will free all memory associated with the result identifier result.

mysql_free_result() only needs to be called if you are concerned about how much memory is being used for queries that return large result sets. All associated result memory is automatically freed at the end of the script's execution.

Parameters

result

The result resource that is being evaluated. This result comes from a call to mysql_query().

Return Values

Returns TRUE on success or FALSE on failure.

If a non-resource is used for the result, an error of level E_WARNING will be emitted. It's worth noting that mysql_query() only returns a resource for SELECT, SHOW, EXPLAIN, and DESCRIBE queries.

Examples

Example #1 A mysql_free_result() example

<?php
$result 
mysql_query("SELECT id,email FROM people WHERE id = '42'");
if (!
$result) {
    echo 
'Could not run query: ' mysql_error();
    exit;
}
/* Use the result, assuming we're done with it afterwards */
$row mysql_fetch_assoc($result);

/* Now we free up the result and continue on with our script */
mysql_free_result($result);

echo 
$row['id'];
echo 
$row['email'];
?>

Notes

Note:

For backward compatibility, the following deprecated alias may be used: mysql_freeresult()

See Also

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User Contributed Notes 7 notes

up
7
webmaster at bluesting dot co dot za
3 years ago
mysql_query() also returns a resource for "OPTIMIZE TABLE" statements!
up
2
Anonymous
7 years ago
If you're seeing warnings like "Warning: Unknown: 6 result set(s) not freed. Use mysql_free_result to free result sets which were requested using mysql_query() in Unknown on line 0" and want to turn them off, set mysql.trace_mode = Off in your php.ini
up
-1
webmaster at wforums dot net
6 years ago
I agree with Joachim Kruyswijk (posted on 14-Jun-2005 11:42). I just did the test on my beta version of my new site (who needs to get dynamically news and user login from a database) and i use 1000kb less memory when i do not use mysql_free_result. I guess it is because the data it needs to load are not that large (for news: date, short description and for the user login: username, password). It may only be in the user control panel that it will be more, but since that isn't developed totally yet, i'll have to test :p
up
-2
admin at ifyouwantblood dot de
6 years ago
yes this function may increase the memory usage if you use unbuffered querys and if you have not fetched all the data from mysql. in this case the mysql api has a problem: you want to free the result but do not want to close the connection. now mysql will only accept another query if all data has been fetched, so the api now must fetch the rest of the data when calling mysql_free_result().

so only use unbuffered querys if you fetch all the data (and need it).
up
-2
Joachim Kruyswijk
9 years ago
Using this function may actually increase the amount of memory used. In my case, the script used 208 bytes less memory when *not* using mysql_free_result().
Check for yourself: call memory_get_usage() at the end of the script.
up
-5
macronesia at macronesia dot net
9 years ago
You not need to use this if you are using PHP 4.

The comment below this comment may explain why it's actually costing more memory.
up
-6
mdeininger at jyujin dot de
9 years ago
yes, i encountered that too. as far as i could tell, that's because the script is stored in memory after being compiled and that's as much more memory as it needs for a call to that function.

if you always get lotsa data in your results, using this function will decrease memory usage tho, unless you use non-buffered queries (which are preferable unless you absolutely *have* to use mysql_seek(), or you need to do another query while the last one hasn't finished reporting back, as they can provide a small speedup)
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