How to obtain PHP memory usage

Source: Internet
Author: User
This article describes how to obtain the PHP memory usage. if you are interested, refer to the PHP built-in function memory_get_usage () to return the memory size currently allocated to the PHP script, the unit is byte ). In actual WEB development, these functions are very useful. we can use them to Debug PHP code performance.
The memory_get_usage () function returns the memory usage, the memory_get_peak_usage () function returns the memory usage peak, and the getrusage () function returns the CPU usage. Note that these functions must be run on Linux.
Let's look at an example:

Echo 'start memory :'. memory_get_usage (), ''; $ tmp = str_repeat ('hello', 1000); echo 'memory after running :'. memory_get_usage (), ''; unset ($ tmp); echo 'back to normal memory :'. memory_get_usage ();

Output result:
Memory start: 147296
Memory after running: 152456
Back to normal memory: 147296
In this example, we use str_repeat () to repeat the string "hello" for 1000 times, and finally compare the memory size consumed before and after. The preceding example shows that to reduce memory usage, you can use the unset () function to delete unnecessary variables. Similarly, the mysql_free_result () function can be used to release the memory occupied by the query when we no longer need to query the result set of the data.
The memory_get_usage () function also has a parameter $ real_usage with a Boolean value. If this parameter is set to TRUE, the real memory size allocated by the system is obtained. If this parameter is not set or set to FALSE, the memory usage reported by emalloc () is used.
In actual WEB development, you can use PHP memory_get_usage () to compare the memory usage of each method and select the method that occupies a small amount of memory.
The number of bytes returned by the function memory_get_usage (), in bytes (s )).

The following custom function converts the number of bytes to MB, which is easier to read:

function memory_usage() {  $memory  = ( ! function_exists('memory_get_usage')) ? '0' : round(memory_get_usage()/1024/1024, 2).'MB';  return $memory; } 

Common debugging methods for detecting PHP code performance include:
Memory_get_usage can be used to analyze memory usage.
You can use the microtime function to analyze the program execution time.

I hope this article will help you learn how php gets the memory usage.

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