A substring operation does not accept a String as a character index

Affected Puppet, Ruby, OS and module versions/distributions

• Puppet: 5.5.2
• Module version: 5.3.0
• Ubuntu 16.04 (both master and agent)

How to reproduce (e.g Puppet code you use)

class { '::php::globals':
    php_version => '7.2'
  } -> class { '::php':
    ensure         => latest,
    manage_repos   => true,
    fpm            => true,
    composer       => true,
    dev            => false,
    pear           => false,
    phpunit        => false,
    package_prefix => 'php7.2-',
    settings   => {
      'PHP/max_execution_time'  => '300',
      'PHP/memory_limit'        => '128M',
      'PHP/post_max_size'       => '100M',
      'PHP/upload_max_filesize' => '100M',
      'Date/date.timezone'      => 'America/Sao_Paulo',
    },
    extensions => {
      pgsql => {
        package_prefix => 'php7.2-',
      },
      gd => {
        package_prefix => 'php7.2-',
      },
      xml => {
        package_prefix => 'php7.2-',
      },
      curl => {
        package_prefix => 'php7.2-',
      },
      mbstring => {
        package_prefix => 'php7.2-',
      },
      mysql => {
        package_prefix => 'php7.2-',
      },
      intl => {
        package_prefix => 'php7.2-',
      },
      gmp => {
        package_prefix => 'php7.2-',
      }
    }
  }

What are you seeing

On agents I get

Error: Could not retrieve catalog from remote server: Error 500 on SERVER: {"message":"Server Error: Evaluation Error: A substring operation does not accept a String as a character index. Expected an Integer (file: /etc/puppetlabs/code/environments/production/modules/php/manifests/globals.pp, line: 20, column: 39) on node uat-ws1","issue_kind":"RUNTIME_ERROR"}
Warning: Not using cache on failed catalog
Error: Could not retrieve catalog; skipping run

What behaviour did you expect instead

The manifest to be applied correctly.

Start with modules/php/manifests/globals.pp at line 20 and reproduce the catalog compilation using the Puppet manifest shown in the issue. Trace the substring operation's character index handling and verify that the manifest applies successfully without the String-index evaluation error.