The php function memory_get_usage() checks the memory currently allocated to PHP scripts

echo memory_get_usage(), ''; // 313864
$tmp = str_repeat('http://www.nowamagic.net/', 4000);
 echo memory_get_usage(), ''; // 406048
unset($tmp);
echo memory_get_usage(); // 313952
?>

behind the above program The comments represent their output (unit is byte(s)), which is the memory used by the PHP script at that time (excluding the memory occupied by the memory_get_usage() function itself).

As can be seen from the above example, in order to reduce memory usage, you can use the PHP unset() function to delete variables that are no longer needed. Similar ones include: PHP mysql_free_result() function, which can clear the result set obtained by querying the database that is no longer needed, so that more available memory can be obtained.

PHP memory_get_usage() function can also have a parameter, $real_usage, whose value is a Boolean value. The default is FALSE, which means that the obtained memory usage does not include the memory occupied by this function (PHP memory manager); when set to TRUE, the obtained memory does not include the memory occupied by this function (PHP memory manager).

In actual programming, you can use the memory_get_usage() function to compare the memory occupied by each method to choose which method takes up less memory.

Post a practical function:

if (!function_exists('memory_get_usage'))
{
/**
+------------------------------------------------ ----------
* Get memory usage
+-------------------------------- --------------------------
* @return integer
+----------------- ----------------------------------------
*/
function memory_get_usage()
{
$pid = getmypid();
if (IS_WIN)
{
 exec('tasklist /FI "PID eq ' . $pid . '" /FO LIST', $output);
return preg_replace('/[^0-9]/', '', $output[5]) * 1024;
}
else
{
exec("ps -eo%mem,rss,pid | grep $pid", $output);
$output = explode(" ", $output[0]);
return $ output[1] * 1024;
}
}
}

Another example of using a function:

//memory_get_usage();
$m1 = memory_get_usage();
echo ' m1:',$m1;//58096
$a = 'hello ';
$b = str_repeat($a,1000);
$m2 = memory_get_usage();
echo ' m2:',$m2;//63424
unset($b);
$ m3 = memory_get_usage();
echo ' m3:',$m3;//58456
?>