PHP Form Builder's Material Forms can be built with Bootstrap 4 or Materialize framework.

Bootstrap Material Forms

• Bootstrap 4 is the framework used as the main css on your page
• Material Design is a customized version of Materialize framework containing only the minimal css/js required for forms.
• These forms are using PHP Form Builder's materialize plugin

 

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Pure Material Forms

• Materialize is the framework used as the main css on your page
• These forms don't use any extra plugin

 

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Detailed explanations here: Material Design Forms