Codeigniter db class truncating text on insert - php

Question

I have a codeigniter controller that receives json content from an API and inserts it to a mysql longtext field unchanged.
Everything's been running smoothly for a while, but recently i've been noticing some of the content is being truncated. Here are two examples.
The table being inserted has three fields
id int
data longtext
date_added datetime
I am receiving the data and directly adding it to the database using the active record insert function. It looks like that
$this->db->insert('received', array('data' => $data, 'date_added' => date('Y-m-d H:i:s')));
Using the profiler, i monitored the queries and found two faulty ones:
INSERT INTO `received` (`data`, `date_added`) VALUES ('{\"status\":{\"lastMaintenanceAt\":0000,\"code\":304,\"period\":900},\"items\":[{\"permalinkUrl\":\"http://example.com\",\"updated\":0000,\"postedTime\":0000,\"summary\":\"Man\'s guarantees are like his words.\",\"title\":\"By: John\",\"content\":\"<p>Man’s guarantees are like his words.</p>\",\"id\":\"http://example.com\",\"actor\":{\"permalinkUrl\":\"\",\"displayName\":\"John\"}}],\"title\":\"Comments on: Banker refuses to give ‘Written Guarantee’\"}', '2012-04-08 00:28:29')
and
INSERT INTO `received` (`data`, `date_added`) VALUES ('{\"status\":{\"code\":304,\"period\":900,\"feed\":\"http://example.com\"},\"items\":[],\"title\":\"Comments on: Making her cry…\"}', '2012-04-08 00:49:35')
The queries seems alright. But only part of the JSON is making it to the table in the first case, it is truncated after "[...] refuses to give" and in the second after making her cry.
The queries are not returning an error and the date is being inserted properly. Moreover, if i copy the queries and execute them in a mysql command prompt, they will insert the full text.
These queries a one a few of hundreds of other successful ones.
Any idea what might be the problem?
thank you

Answer 1

All of the faulty queries share one thing in common: they've got "special characters" which MS Word inserts, e.g. ‘, ’ and …. If you can convert / remove these, then your problems should go away.
Update
For a CodeIgniter solution to this, you could load the Text Helper library and then use the ascii_to_entities function on any strings, e.g.
$this->load->helper('text');
$desc = ascii_to_entities($desc);