UNSW ProgComp: Problem 3 - 2008

<?php
//word ladder checker

$input = <<<END
8
14 frown crown croon crook crock chock shock shack stack stick stalk stale stile smile
7 brown grown groan groat great greet green
16 great greet greed breed bread bred bleed blend bland blank black slack stack stalk stall small
2 hero zero
11 cain fain fail fall fill full fell fill file aile able
7 o i c u r m t
4 batt bait bai1 ba11
7 less loss lose lost love move more
END;

$input = explode("\n", $input);
array_shift($input);
$letters = array('a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z');

foreach($input as $key => $value){
    $temp = explode(" ", $value);
    array_shift($temp);
    foreach($temp as $key3 => $value3){
        if($key3 == count($temp)-1){
            echo "$value3\n  ";
        }else{
            echo "$value3 ";
        }
    }
    $history = array();
    foreach($temp as $key2 => $value2){
        if($key2 == 0){
            $length = strlen($value2);
            $history[] = $value2;
        }else{
            if($value2 != strtolower($value2)){
                //string is not all lower case
                echo "contains other than lower-case letters \"$value2\"\n";
                break;
            }
            if($length != strlen($value2)){
                //string is on inconsistent length
                echo "Inconsistent word length for \"$value2\"\n";
                break;
            }
            if(levenshtein($value2, $history[$key2-1]) != 1){
                //more than 1 changes
                echo "Too many changes to produce \"$value2\"\n";
                break;
            }
            if(in_array($value2, $history)){
                //string is already in the array
                echo "Repeated word \"$value2\"\n";
                break;
            }
            if(str_replace($letters, '', $value2) != ''){
                //string contains non-letters
                echo "Non-letters in \"$value2\"\n";
                break;
            }
            $history[] = $value2;
        }
        if($key2 == count($temp)-1){
            echo "Feasible\n";
        }
    }
}