PHP set private property value using reflection. This allows you to set a private property value from outside the object, great for PHPUnit testing.

gistfile1.php

<?php

$a = new A();
$reflection = new \ReflectionClass($a);
$property = $reflection->getProperty('privateProperty');
$property->setAccessible(true);
$property->setValue($a, 'new-value');

echo $a->getPrivateProperty();
//outputs:
//new-value

You can also use a closure binding:

class A {
  private string $name;
}

$a = new A();

$setter = (function (string $property, mixed $value): void {
    $this->{$property} = $value;
})->bindTo($a, $a);
$setter('name', 'Name');