I just realized something that never occurred to me before - every
property is actually stored as a hash.
This test-script will demonstrate:
<?php
define('NUM_TESTS', 1000);
$before = memory_get_usage(true);
$test = array();
class Foo
{
public $aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa;
public $bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb;
public $cccccccccccccccccccccccccccccccccccccccccccccccccccc;
public $dddddddddddddddddddddddddddddddddddddddddddddddddddd;
}
$bytes = 0;
for ($i=0; $i<NUM_TESTS; $i++) {
$foo = new Foo;
$foo->aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa = 'a';
$foo->bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb = 'b';
$foo->cccccccccccccccccccccccccccccccccccccccccccccccccccc = 'c';
$foo->dddddddddddddddddddddddddddddddddddddddddddddddddddd = 'd';
$bytes += 4;
$test[] = $foo;
}
$after = memory_get_usage(true);
header('Content-type: text/plain');
echo ($after-$before).' bytes used; '.$bytes.' bytes of information stored.';
Output is this:
786432 bytes used; 4000 bytes of information stored.
I know this an extreme example, I just did it to see if what I
suspected was actually correct.
How come it's necessary to store the property-names of every property
in every object? For properties that have been defined in classes, why
can't they be stored in a more efficient manner? (using lookup tables)
I know the nature of PHP is dynamic, and I know that dynamic
properties would have to be stored in a key/value form internally...
but if you look at modern PHP software, dynamic properties is actually
something very few people use.
My suspicion is that all this memory-overhead has performance
implications as well? Allocating and deallocating memory for all of
these repeated property-names, it can't be very efficient?
I don't know much about the inner workings of PHP or C in general, but
if the property-names are in deed stored repeatedly, and if the
string-type uses a pointer, wouldn't it possible to point all of the
property-name strings to same address in memory, sharing the
property-name strings, instead of storing them repeatedly?
Just a thought...
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