Do variables occupy memory in php?

One way to store data in php is the amount that i can change. This method is to open up a space in memory that can store data. , give this space a name, and the space at this time can be called a variable. This value can be changed during operation

The name of the current space is the variable name, and the data (eight data types) of the current space is called the variable value

Example: (Recommended learning: PHP video tutorial)

php version is 7.2

<?php
echo memory_get_usage() , &#39;<br>&#39;;
$start = memory_get_usage();
$a = Array();
for ($i=0; $i<1000; $i++) {
$a[$i] = $i + $i;
}
$mid = memory_get_usage();
echo memory_get_usage() , &#39;<br>&#39;;
for ($i=1000; $i<2000; $i++) {
$a[$i] = $i + $i;
}
$end = memory_get_usage();
echo memory_get_usage() , &#39;<br>&#39;;
echo &#39;argv:&#39;, ($mid - $start)/1000 ,&#39;bytes&#39; , &#39;<br>&#39;;
echo &#39;argv:&#39;,($end - $mid)/1000 ,&#39;bytes&#39; , &#39;<br>&#39;;
echo &#39;Memory:&#39;, ($mid - $start)/1024 ,&#39;k&#39; , &#39;<br>&#39;;
echo &#39;Memory:&#39;,($end - $mid)/1024 ,&#39;k&#39; , &#39;<br>&#39;;
输出是:
389336
418056
442632
argv:28.72bytes
argv:24.576bytes
Memory:28.046875k
Memory:24k

Return to the current allocation The amount of memory given to your PHP script, in bytes.

It is roughly understood that an integer array of 1000 elements takes up 28k of memory, and each element occupies an average of 28 bytes

The results returned by memory_get_usage() are not all occupied by the array, but also To include some structures allocated by PHP

, the array generated by the built-in function may be closer to the real space:

<?php
$start = memory_get_usage();
$a = array_fill(0, 10000, 1);
$mid = memory_get_usage(); //10k elements array;
echo &#39;argv:&#39;, ($mid - $start )/10000,&#39;byte&#39; , &#39;<br>&#39;;
echo &#39;Memory:&#39;, ($mid - $start)/1024 ,&#39;k&#39; , &#39;<br>&#39;;
$b = array_fill(0, 10000, 1);
$end = memory_get_usage(); //10k elements array;
echo &#39;argv:&#39;, ($end - $mid)/10000 ,&#39;byte&#39; , &#39;<br>&#39;;
echo &#39;Memory:&#39;,($end - $mid)/1024 ,&#39;k&#39; , &#39;<br>&#39;;
得到:
argv:54.5792byte
argv:54.5784byte

argv:39.736byte
Memory:388.046875k
argv:39.736byte
Memory:388.046875k

It is roughly understood that an integer array of 10,000 elements takes up 388k of memory, From this result, it seems that one array element takes up about 39 bytes.

The above is the detailed content of Do variables occupy memory in php?. For more information, please follow other related articles on the PHP Chinese website!