ACF model via php example ~ https://www.advancedcustomfields.com/resources/register-fields-via-php

acf-models.php

<?php

add_action('acf/init', 'register_post_fields');

function register_post_fields () {
  $location = [
    [
      [
        'param' => 'post_type',
        'operator' => '==',
        'value' => 'post'
      ]
    ]
  ];

  $fields = [
    [
      'key' => 'field_1',
      'label' => 'Subtitle',
      'name' => 'subtitle',
      'type' => 'text'
    ],
    [
      'key' => 'field_2',
      'label' => 'Some URL',
      'name' => 'some_url',
      'type' => 'url'
    ]
  ];

  acf_add_local_field_group([
    'key' => 'group_post_1',
    'title' => 'Post Fields',
    'fields' => $fields,
    'location' => $location
  ]);
}