getter.php

<?php

class Foo {

    public string $foo = 'foo';

    public function setString($value): void {
        $this->foo = $value;
    }

    public function getString(): string {
        return $this->foo;
    }
}

$foo = new Foo();
$bar = null;

$iter = 10_000_000;

while(--$iter) {
    $foo->setString("foo" . $iter);
    $bar = $foo->getString();
}

hooks.php

<?php

class Foo {

    private string $_foo;

    public string $foo {
        get => $this->_foo;
        set { $this->_foo = $value; }
    }
}

$foo = new Foo();
$bar = null;

$iter = 10_000_000;

while(--$iter) {
    $foo->foo = "foo" . $iter;
    $bar = $foo->foo;
}

public.php

<?php

class Foo {

    public string $foo = 'foo';
}

$foo = new Foo();
$bar = null;

$iter = 10_000_000;

while(--$iter) {
    $foo->foo = "foo" . $iter;
    $bar = $foo->foo;
}