Convert to PDO regexp bind error

Convert to PDO regexp bind error

I'm trying to convert from mysql to using PDO. I'm stuck on this error:
For the most part I got it working except when it comes to binding the
variable.
Fatal error: Call to a member function bindParam() on a non-object in
Here is what I tried:
global $keyword;
$_link = new PDO("mysql:host=$host;dbname=$db_name", "$username",
"$password");
$_query = sprintf("SELECT SQL_CALC_FOUND_ROWS * FROM PLD_ANINJA WHERE
`Text` REGEXP CONCAT('[[:<:]]',:keyword,'[[:>:]]') LIMIT %d,%d",
SmartyPaginate::getCurrentIndex(), SmartyPaginate::getLimit());
$_query->bindParam(':keyword',$keyword, PDO::PARAM_STR);
$_query->execute();
Here is what worked originally:
global $keyword;
$_query = sprintf("SELECT SQL_CALC_FOUND_ROWS * FROM PLD_ANINJA WHERE
`Text` REGEXP '[[:<:]]" . $keyword . "[[:>:]]' LIMIT %d,%d",
SmartyPaginate::getCurrentIndex(), SmartyPaginate::getLimit());