header.php

 <!DOCTYPE html>
  <html>
    <head>

      <meta charset="utf-8">
      <title> Sistema de cadastro de clientes</title>
      <!--Import Google Icon Font-->
      <link href="https://fonts.googleapis.com/icon?family=Material+Icons" rel="stylesheet">
      <!--Import materialize.css-->
       <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/materialize/1.0.0/css/materialize.min.css">

      <!--Let browser know website is optimized for mobile-->
      <meta name="viewport" content="width=device-width, initial-scale=1.0"/>
    </head>

    <body>