Test a string is isogram of any order/Get order of isogram

find_isogram_order.php

function find_isogram_order($word) {
  if(empty($word))
    return;
    
  foreach(str_split(strtolower($word)) as $char) {
      if(is_numeric($char)) {
        return;
      }
      if(!isset($sequence[$char])) {  
        $sequence[$char] = 1;
      } 
      else {
        $sequence[$char]++;
      }
  }
  if(count(array_flip($sequence)) === 1) {
    return current($sequence);
  }
}

$values = [
  "",
  "1111",
  "1111ssss",
  "Dermatoglyphics",
  "aba",
  "moOse",
  "booBsB",
  "booB",
  "Caucasus",
  "geggee",
  "vexes"
];
foreach($values as $value) {
  if($order = find_isogram_order($value) and is_numeric($order)) {
    echo "$value, order: $order".PHP_EOL;
  }
}

find_wordset_isogram_order.php

// repl https://repl.it/GKMW/4

function find_isogram_order($word) {
  if(empty($word))
    return;
    
  foreach(str_split(strtolower(str_replace(' ', '', $word))) as $char) {
      if(is_numeric($char)) {
        return;
      }
      if(!isset($sequence[$char])) {  
        $sequence[$char] = 1;
      } 
      else {
        $sequence[$char]++;
      }
  }
  if(count(array_flip($sequence)) === 1) {
    return current($sequence);
  }
}

function find_wordset_isogram_order(array $wordset = array()) {
  $orders = [];
  foreach($wordset as $word) {
    $order = find_isogram_order($word);
    if($order > 0) {
      $orders[$word] = $order;
    }
    else {
      $order[$word] = 0;
    }
  }
  return $orders;
}

$wordset = [
  'myth duck',
  'myth duck verb',
  'myth duck verb gasp',
  'myth duck verb gasp jinx',
  'myth duck verb gasp jinx wolf',
  'abdest',
  'abdest chi',
  'abdest chi group',
  "",
  "1111",
  "1111ssss",
  "Dermatoglyphics",
  "aba",
  "moOse",
  "booBsB",
  "booB",
  "Caucasus",
  "geggee",
  "vexes"
];
var_dump(find_wordset_isogram_order($wordset));

is_isogram.php

function is_isogram($word) {
  if(empty($word))
    return false;
    
  foreach(str_split(strtolower($word)) as $char) {
      if(is_numeric($char)) {
        return false;
      }
      if(!isset($sequence[$char])) {  
        $sequence[$char] = 1;
      } 
      else {
        $sequence[$char]++;
      }
  }
  if(count(array_flip($sequence)) === 1) {
    return true;
  }
  return false;
}

$values = [
  "",
  "1111",
  "1111ssss",
  "Dermatoglyphics",
  "aba",
  "moOse",
  "booBsB",
  "booB",
  "Caucasus",
  "geggee",
  "vexes"
];
foreach($values as $value) {
  if(is_isogram($value)) {
    echo $value.PHP_EOL;
  }
}