Abstract Transformer class for PHP

TransformerAbstract.php

<?php

/**
 * Class TransformerAbstract
 * contains functions for validating fields
 *
 * @package Drupal\streamtime
 */
abstract class TransformerAbstract {

  /**
   * map input property names with transformed output keys
   * @var array
   */
  protected $property_map = [];


  /**
   * input to transform class
   * @var array
   */
  protected $input = [];
  /**
   * fields that are required
   * @var array
   */
  protected $requiredFields = [];

  /**
   * validates $input against a required set of fields
   *
   * @return array|bool
   */
  public function validate() {

    $valid = true;
    foreach($this->requiredFields as $field) {
      $sub_fields = explode('.', $field);
      $inner_array = false;
      foreach($sub_fields as $sub_field) {
        if ($inner_array !== false) {
          $valid = isset($inner_array[$sub_field]);
          $inner_array = ($valid === true) ? $inner_array[$sub_field] : $inner_array;
        } else {
          $valid = isset($this->input[$sub_field]);
          $inner_array = ($valid === true) ? $this->input[$sub_field] : false;
        }
        if ($valid !== true) {
          $message =  sprintf('The required field %s was not found', $field);

          $valid = [
            'error' => true,
            'message' => $message
          ];
          break;
        }
      }
    }

    return $valid;
  }

  /**
   * gets a value of a field
   * @param $property
   *
   * @return mixed
   */
  public function getValue($property) {
    $fields = explode('.', $property);
    $object = $this->input;
    foreach ($fields as $field) {
      $object = $object[$field];
    }
    return $object;
  }

  /**
   * creates the transformed output
   * @return array
   */
  public function output () {
    $output = [];
    foreach ($this->input as $property => $value) {
      if (in_array($property, $this->requiredFields)) {
        $value = $this->getValue($property);
        $field_name = $this->getFieldName($property);
        $output[$field_name] = $value;
      }
    }
    return $output;
  }


  public function getFieldName($property) {
      return (isset($this->property_map[$property])) ? $this->property_map[$property] : $property;
  }

  /**
   * TransformerAbstract constructor.
   *
   * @param $input
   */
  public function __construct($input) {
      $this->input = $input;
  }

}