Function upload

function upload() {

  $namaFile = $_FILES['gambar']['name'];
  $tmpName = $_FILES['gambar']['tmp_name'];
  $ukuranFile = $_FILES['gambar']['size'];
  $error = $_FILES['gambar']['error'];


  // cek tidak ada gambar yang di upload
  if ( $error === 4 ) {
    echo "<script>
    alert('Pilih gambar terlebih dahulu')
          </script>";
          return false;
  }

  //cek yang di upload hanya gambar
  $ekstensiGambarValid = ['jpg', 'jpeg', 'png'];
  $ekstensiGambar = explode('.', $namaFile);
  $ekstensiGambar = strtolower(end($ekstensiGambar)) ;
  if( !in_array($ekstensiGambar, $ekstensiGambarValid)) {

    echo "<script>
    alert('Yang anda Upload bukan Gambar')
          </script>";
          return false;
}
  if ($ukuranFile > 1000000 ) {
    echo "<script>
    alert('Ukuran Gambar terlalu besar!');
          </script>";
          return false;
  }
// lolos upload
// generate nama gambar baru
  $namaFileBaru = uniqid();
  $namaFileBaru .= '.';
  $namaFileBaru .= $ekstensiGambar;

  move_uploaded_file($tmpName, '../upload/image/' . $namaFileBaru);
  return $namaFileBaru;
}