Optimize PHP code (concatenating words with a comma, removing last comma)

I've used this method almost always to get "Word1, Word2, Word3" from an array('Word1', 'Word2', 'Word3')

Is it the shortest or acceptable method? Any better solution?

$sentence = '开发者_如何转开发';
foreach ($words as $word) {
    $sentence .= $word . ", ";
}
$final_sentence = substr($sentence, 0, -2);

echo $final_sentence; //outputs contents of $words array separated by ,

<?php
$sentence = implode(', ', $words);
?>

Use implode:

$final_sentence = implode(", ", $words);

$final_sentence = implode(', ',$words)