Functional Query Builder

<?php
  function make_query_builder_select(): Closure {
    $memory = [
      'tables' => []
    ];

    $builder = function(string $instruction) use (&$memory, &$builder) {
      $instructionParameters = explode(' ', $instruction);
      $instruction = array_shift($instructionParameters);

      switch ($instruction) {
        case 'from':

          break;

        default:
          throw new Exception("Unknown instruction '{$instruction}'!");
      }
      return $builder;
    };

    return $builder;
  }