<?php

//Eg- Panagram -  The quick brown fox jumps over the lazy dog

$str = "The quick brown fox jumps over the lazy dog";

$wordarr = array();

for($i=0;$i<strlen($str);$i++){
    
    $word = strtoupper($str[$i]);
    
    if((!in_array($word,$wordarr)) && ($word >= 'A') && ($word <= 'Z')){
        array_push($wordarr,$word);
    }
}

$missed_words = '';
$cmparr = range('A','Z');

$arraydiff = array_diff($cmparr,$wordarr);

$missed_words = implode('',$arraydiff);

echo $missed_words;