Detailed explanation of getting memory usage in PHP

This article will explain in detail how to obtain memory usage in php.

PHP built-in function memory_get_usage() can return the amount of memory currently allocated to the PHP script, in bytes. In actual WEB development, these functions are very useful, and 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 peak memory usage, and getrusage() returns the CUP usage. But please note that these functions need to run on Linux.

Let’s look at an example:

echo'开始内存：'.memory_get_usage(),'';
$tmp=str_repeat('hello',1000);
echo'运行后内存：'.memory_get_usage(),'';
unset($tmp);
echo'回到正常内存：'.memory_get_usage();

Output result:

Starting memory: 147296

After running memory: 152456

Return to normal memory: 147296

In the example, we use str_repeat() to repeat the string "hello" 1000 times, and finally compare the memory size consumed before and after. As can be seen from the above example, in order to reduce memory usage, you can use the unset() function to delete variables that are no longer needed. Similar to the mysql_free_result() function, when we no longer need the result set obtained by querying data, we can use it to release the memory occupied by the query.

The function memory_get_usage() can also have a parameter, $real_usage, whose value is a Boolean value. If set to TRUE, obtains the actual memory size allocated by the system. If unset or set to FALSE, emalloc() will report the amount of memory used.

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

The number of bytes returned by function memory_get_usage() (unit is byte(s)). The following custom function converts the number of bytes into MB for easier reading:

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

Commonly used methods for debugging and detecting PHP code performance are:

memory_get_usage can analyze the memory footprint.

Use the microtime function to analyze the program execution time.

This article explains in detail the memory usage of php. For more related content, please pay attention to the php Chinese website.

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