How to get memory usage method 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 below:

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:

开始内存：147296 
运行后内存：152456 
回到正常内存：147296

In the example, we use str_repeat() to repeat the string "hello" 1000 times. Finally, To 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: byte(s)). The following custom function converts the number of bytes into MB for easier reading:

function memory_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.

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