escape_str in mysql

[eluser]displaynone[/eluser]
I have been looking for a similar bug, but I don't find it, so I decide to write a new one.
When I try to escape a string using escape_str function, I get incorrect results.
For example:

Code:

$query = $this->db->query('insert into table values (?, ?)', array('value1', 'value2 /\/\/\'));

The query result is:

Code:

insert into table values ('value1', 'value2 /\/\/\')

The error is in the last slash & quote.

The escape_str function is this:

Code:

function escape_str($str)    
{    
  // Escape single quotes
  return str_replace("'", "''", $str);
}

Why do you do this way if exists the function mysql_escape_string?

Thanks for your time and sorry for my english