I've noticed this too.
I've got an IRC bot in PHP, I'm handling SIGINT to clean up before exiting.
With declare(ticks=1] in an included file,
in 5.6.20: triggered near instant
in 7.0.4: can take up to 20 seconds. Near instant after moving declare to the main file. There's also no mention of this change in the migration guide.

We were trying to add a timeout feature to laravel artisan command `queue:work`. But the tests failed in PHP 7.0:
Pull request: https://github.com/laravel/framework/pull/13425

A simpler test case that fails:
https://github.com/halaei/ticks-bug-php-7
https://travis-ci.org/halaei/ticks-bug-php-7/builds/130244558

Code:
#main.php
<?php

declare(ticks=1);
pcntl_signal(SIGALRM, function ($sig) {
    die(0);
});

require_once __DIR__ . '/loop.php';


#loop.php
<?php

pcntl_alarm(2);
while (true) {
    sleep(10);
}


Expected behavior: the code terminates after 2 seconds
Observed behavior: the code will never terminate.

Due to an implementation bug, the declare(ticks=1) directive leaked into different compilation units prior to PHP 7.0. This is not how declare() directives, which are per-file or per-scope, are supposed to work.

Using a single declare(ticks=1) in some class inside a multi-class autoloaded project doesn't make a lot of sense. Even on PHP 5.x declare(ticks=1) would only affect code that is compiled starting from that declaration, which means that depending on the loading order of classes your whole codebase might end up using ticks or maybe only a few classes that were loaded late. (Not to mention that using ticks will make your code many times slower, but that's a different issue.)

For PHP 7.1 we may make automatic pcntl signal handling work without ticks, as we now have a new internal mechanism for handling ordinary timeouts which we can reuse.

As an update on the previous comment: PHP 7.1 supports async signals, see https://wiki.php.net/rfc/async_signals. It looks like pcntl_async_signals() is not documented yet. This allows handling signals without using ticks.