Create a netbeans project (I've not tried it with other debugger front ends) with a file containing the following code.

Stepping a breakpoint at line 5 ( echo "."; ) and then:

Debug file: Ctrl+Shift+F5
Continue: Ctrl+F5
Wait some seconds
Step Into: F7

Then a "Socket Error" should appear. The IDE log says: "Broken Pipe"

<?php

class myTest {

function test() {
    echo ".";
}

}

function a() {

$params = array();
$class = new myTest();
$invoker = new Invoker();
$invoker->invoke(array($class, 'test'), $params);
$invoker->invoke(array($class, 'test'), $params);

}

a();
a();

declare(ticks = 1);
class Invoker
{
public function invoke($callable, array $arguments)
{
pcntl_signal(SIGALRM, array($this, 'callback'), TRUE);
pcntl_alarm(1);

    $result = call_user_func_array($callable, $arguments);

    pcntl_alarm(0);
}

public function callback() { }

}