VersionPress\Database\DbSchemaInfo::getAllReferences PHP Method

    public function getAllReferences()
    {
        $references = [];
        foreach ($this->getAllEntityNames() as $entity) {
            $references[$entity] = $this->getEntityInfo($entity)->getReferencedEntities();
        }
        return $references;
    }

 /**
  * Determines sequence in which entities should be synchronized.
  * It's based on their dependencies on other entities.
  *
  * @return array
  */
 private function resolveSynchronizationSequence()
 {
     $unresolved = $this->dbSchema->getAllReferences();
     $sequence = [];
     $triedRemovingSelfReferences = false;
     while (count($unresolved) > 0) {
         $resolvedInThisStep = [];
         // 1st step - move all entities with resolved dependencies to $sequence
         foreach ($unresolved as $entity => $deps) {
             if (count($deps) === 0) {
                 unset($unresolved[$entity]);
                 $sequence[] = $entity;
                 $resolvedInThisStep[] = $entity;
             }
         }
         // 2nd step - update unresolved dependencies of remaining entities
         foreach ($resolvedInThisStep as $resolvedEntity) {
             foreach ($unresolved as $unresolvedEntity => $deps) {
                 $unresolved[$unresolvedEntity] = array_diff($deps, [$resolvedEntity]);
             }
         }
         // Nothing changed - circular dependency
         if (count($resolvedInThisStep) === 0) {
             if (!$triedRemovingSelfReferences) {
                 // At first try to remove all self-references as they have to run in 2-pass sync anyway
                 $triedRemovingSelfReferences = true;
                 foreach ($unresolved as $unresolvedEntity => $deps) {
                     $unresolved[$unresolvedEntity] = array_diff($deps, [$unresolvedEntity]);
                 }
             } else {
                 // Simply eliminate dependencies one by one until it is resolvable
                 reset($unresolved);
                 $firstEntity = key($unresolved);
                 array_pop($unresolved[$firstEntity]);
             }
         }
     }
     return $sequence;
 }