Yii2's get() implementation throws an exception when get is called with a non-existing $name. It seems that XDebug calls the __get function to obtain the value for a private variable of the base class and the resulting exception is not caught.

Possibly related: Clicking open a Closure also results in an similar exception ("Closue object cannot have properties"). Please let me know if you would like an extra ticket for that.

Code example (no dependencies):
<?php

class BaseClass {
protected $protected = [1, 2, 3];
private $private = ['a', 'b', 'c'];
}

class DerivedClass extends BaseClass {
function __get($name)
{
throw new \Exception('Derived class getter called with: ' . $name);
}
}

try {
$test = new DerivedClass();
echo "Statement to break on."; // Breakpoint here
}
catch (\Exception $e) {
echo $e->getMessage();
}