Use reflection to get an array of both visible & hidden object properties. Handles nested objects recursively.

extract-all-object-props-to-array.php

<?php

function extractAllObjectPropsToArray( $object )
{
  $properties = [];
  $reflection = new ReflectionClass( $object );
  
  foreach ( $reflection->getProperties() as $property )
  {
    $property->setAccessible( TRUE );
    
    $propName  = $property->getName();
    $propValue = property_exists( $object, $propName )
      ? $property->getValue( $object )
      : NULL;
    
    switch ( TRUE )
    {
      case is_array( $propValue ):
        $properties[ $propName ] = [];
        
        foreach ( $propValue as $value )
        {
          $properties[ $propName ][] = is_object( $value )
            ? extractAllObjectPropsToArray( $value )
            : $properties[ $propName ][] = $value;
        }
        break;
      case is_object( $propValue ):
        $properties[ $propName ] = extractAllObjectPropsToArray( $propValue );
        break;
      default:
        $properties[ $propName ] = $propValue;
        break;
    }
  }
  
  return $properties;
}