Check if the edit distance between two words is 1

gistfile1.php

<?php
/*
d = ['cat', 'cats', 'bat', 'beetle']

similar(q, d):
    ....
    
returns all words from d with edit distance 1

similar('cat', d) --> ['cat', 'cats', 'bat']


replace any letter in q
add a letter anywhere in q
drop any letter in q

'cat' --  26 * 3 + 26 * 4 + 3 
*/

// str2 is always longer

function dist_is_one($str1, $str2) {
    $diff = abs(strlen($str1) - strlen($str2));
    
    if ($diff > 1){
        return false;
    }
    
    // assuming str2 is the longer one
    for ($i = 0; $i < strlen($str1); $i++)
    {
        if ($str1[$i] != $str2[$i])
        {
           // cat, bat
            // try a replace
            $newStr = $str1; // TODO: Does this make a copy?
            $newStr[$i] = $str2[$i];
            if ($newStr == $str2)
                return true;
                       
            // Insertion
           // at, bat -> bt, bat ct cat 
            $newStr = $str1;
            $newStr = substr($newStr, 0, $i).$str2[$i].substr($newStr, $i);
            if ($newStr == $str2) 
                return true;
                
            return false;
        }
    }
    
    return true;
}


print_p(dist_is_one('ct', 'cat'));
print_p(dist_is_one('bat', 'cat'));
print_p(dist_is_one('adf', 'cat'));
print_p(dist_is_one('bdt', 'cat'));
print_p(dist_is_one('baaale', 'beetle'));
echo "<br />";
print_p(dist_is_one('', 'c'));
print_p(dist_is_one('', 'lol'));
print_p(dist_is_one('', ''));
print_p(dist_is_one('a', 'a'));

function print_p($ele) {
    print var_dump($ele) ."<br />";
}
?>