TYPO3 Core

When connecting a signal with a slot, being the slot an object instance with complex structure (many nested elements), \TYPO3\CMS\Extbase\SignalSlot\Dispatcher->connect throws the exception:

Fatal error: Nesting level too deep - recursive dependency?

when checking if signal-slot connection already exists:

if (!is_array($this->slots[$signalClassName][$signalName]) || !in_array($slot, $this->slots[$signalClassName][$signalName])) {
   $this->slots[$signalClassName][$signalName][] = $slot;
}

The exceptions occurs at in_array(...), which happens when connecting the second (and next) slot to the same signal.

This happens because slot is not strictly compared when doing the in_array search as mentioned here: https://stackoverflow.com/questions/3834791/fatal-error-nesting-level-too-deep-recursive-dependency

Setting the strict flag on the in_array solves the problem:

if (!is_array($this->slots[$signalClassName][$signalName]) || !in_array($slot, $this->slots[$signalClassName][$signalName], true)) {
   $this->slots[$signalClassName][$signalName][] = $slot;
}