$re = '/(\\\\s|[\"\'\\\\([{]|^)id\s?((?:[1-9]|10)\.(?:[1-9]|[1-9][0-9]|100))(["\':.;,!?…\]})]|\s|$)/im';
$str = 'id1.1
id1.10
id10.100
id10.1
id 1.1
# The following should not match
id0.1
id1.0
id11.1
id1.200
id1.101
id1.1000';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
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