Anton Sukhachev
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PHP var_sizeof()

The library provides functions to get the size of any PHP variable in bytes
It should be a more accurate tool for calculating the total size of a PHP variable than memory_get_usage(), but it has limitations.

How it works

The var_sizeof() and var_class_sizeof() functions use FFI to access the internal structures of PHP variables.
They calculate the size of internal structures like zval, _zend_array, _zend_object, etc., along with any additional allocated memory for these structures.
However, they do not account for the memory used by handlers, functions, or similar components.

Requirements

Usage 

composer require mrsuh/php-var-sizeof
<?php

require_once __DIR__ . '/vendor/autoload.php';

$int = 1;
printf("variable \$int size: %d bytes\n", var_sizeof($int));

$array = array_fill(0, 100, $a);
printf("variable \$array size: %d bytes\n", var_sizeof($array));

$object = new \stdClass();
printf("variable \$object size: %d bytes\n", var_sizeof($object));
printf("class \$object size: %d bytes\n", var_class_sizeof($object));

var_sizeof vs memory_get_usage

PHP 8.1.2 Linux(x86_64)

type var_sizeof(bytes) memory_get_usage(bytes)
NULL 16 0
boolean(true) 16 0
integer(1) 16 0
double(1.5) 16 0
string("hello world") 27 40
resource 48 416
callable 72 384
array(count: 0, list: true) 336 0
array(count: 100, list: true) 2,128 8,248
array(count: 1,000, list: true) 16,464 36,920
array(count: 10,000, list: true) 262,224 528,440
array(count: 100, list: false) 5,192 8,248
array(count: 1,000, list: false) 41,032 41,016
array(count: 10,000, list: false) 655,432 655,416
EmptyClass{} 72 40
ClassWithArray{"array(count: 0, list: true)"} 408 56
ClassWithArray{"array(count: 100, list: true)"} 2,200 8,304
ClassWithArray{"array(count: 1,000, list: true)"} 16,536 36,976
ClassWithArray{"array(count: 10,000, list: true)"} 262,296 528,496
ClassWithObject{"EmptyClass{}"} 144 96
ArrayIterator{"array(count: 100, list: true)"} 2,264 8,376
ArrayIterator{"array(count: 100, list: false)"} 5,328 40,376
type var_class_sizeof(bytes) var_sizeof(bytes) memory_get_usage(bytes)
EmptyClass{} 1,362 72 40
ClassWithArray{"array(count: 0, list: true)"} 1,494 408 56
ClassWithArray{"array(count: 100, list: true)"} 1,494 2,200 8,304
ClassWithArray{"array(count: 1,000, list: true)"} 1,494 16,536 36,976
ClassWithArray{"array(count: 10,000, list: true)"} 1,494 262,296 528,496
ClassWithObject{"EmptyClass{}"} 1,495 144 96
ArrayIterator{"array(count: 100, list: true)"} 2,437 2,264 8,376
ArrayIterator{"array(count: 100, list: false)"} 2,437 5,328 40,376

Limitations