$re = '/(?<=\b[a-zA-Z]\d[a-zA-Z] \d[a-zA-Z]\d)\s+/m';
$str = '160 Rue, Notre Dame N, Bureau 140, Sainte-Marie, G6E 3Z9 887 Chemin du Bord de l\'Eau, Saint-Henri de Levis, G0R 3E0';
$subst = "\n";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php