Here is a function which should work with the most common of words... It should give you a nice result between 1 (perfect pronounceability according to the rules) to 0.
The following function far from perfect (it doesn't quite like words like Tsunami [0.857]). But it should be fairly easy to tweak for your needs.
<?php
// Score: 1
echo pronounceability('namelet') . "\n";
// Score: 0.71428571428571
echo pronounceability('nameoic') . "\n";
function pronounceability($word) {
static $vowels = array
(
'a',
'e',
'i',
'o',
'u',
'y'
);
static $composites = array
(
'mm',
'll',
'th',
'ing'
);
if (!is_string($word)) return false;
// Remove non letters and put in lowercase
$word = preg_replace('/[^a-z]/i', '', $word);
$word = strtolower($word);
// Special case
if ($word == 'a') return 1;
$len = strlen($word);
// Let's not parse an empty string
if ($len == 0) return 0;
$score = 0;
$pos = 0;
while ($pos < $len) {
// Check if is allowed composites
foreach ($composites as $comp) {
$complen = strlen($comp);
if (($pos + $complen) < $len) {
$check = substr($word, $pos, $complen);
if ($check == $comp) {
$score += $complen;
$pos += $complen;
continue 2;
}
}
}
// Is it a vowel? If so, check if previous wasn't a vowel too.
if (in_array($word[$pos], $vowels)) {
if (($pos - 1) >= 0 && !in_array($word[$pos - 1], $vowels)) {
$score += 1;
$pos += 1;
continue;
}
} else { // Not a vowel, check if next one is, or if is end of word
if (($pos + 1) < $len && in_array($word[$pos + 1], $vowels)) {
$score += 2;
$pos += 2;
continue;
} elseif (($pos + 1) == $len) {
$score += 1;
break;
}
}
$pos += 1;
}
return $score / $len;
}