[Help] auto replace content when post

[Thangvip9x]

Please help me
I have a example
If i post character "a, b, c, d" will auto replace to character "e, f, g, h"
I use hook postbit_display_complete use str_replace and

PHP Code:

$this->post['message'] 


but it only replace message, i want auto replace pagetext from database
This is my plugin

PHP Code:

$post1=array(
'a','b','c' ,'d'
);
$post2=array(
'e','f','g' ,'h'
);
$this->post['message'] = str_replace($post1, $post2, $this->post['message']); 


I used hook postdata_presave with

PHP Code:

$this->post['pagetext'] 


use good, but empty first post when move threads
This is my plugin

PHP Code:

$post1=array(
'a','b','c' ,'d'
);
$post2=array(
'e','f','g' ,'h'
);
$this->post['pagetext'] = str_replace($post1, $post2, $this->post['pagetext']); 


I use hook postbit_display_complete and use

PHP Code:

$post['pagetext'] 


use good but error MySQL when read private message
Please help me write plugin auto replace pagetext from database when post
Thank you very much
This is my plugin i write with hook postbit_display_complete with

PHP Code:

$this->post['pagetext'] 


and

PHP Code:

$this->post['message'] 


use good but error when read private message

PHP Code:

$post1=array(
'a','b','c' ,'d'
);
$post2=array(
'e','f','g' ,'h'
);
$this->post['message'] = str_replace($post1, $post2, $this->post['message']);
$this->post['pagetext'] = str_replace($post1, $post2, $this->post['pagetext']);
$db->query_write("
                    UPDATE ".TABLE_PREFIX."post 
                    SET pagetext = '".$db->escape_string($this->post['pagetext'])."'
                    WHERE postid = ".$post['postid']."
                "); 


If i remove this content in my plugin

PHP Code:

$this->post['pagetext'] = str_replace($post1, $post2, $this->post['pagetext']);
$db->query_write("
                    UPDATE ".TABLE_PREFIX."post 
                    SET pagetext = '".$db->escape_string($this->post['pagetext'])."'
                    WHERE postid = ".$post['postid']."
                "); 


Use good but don't replace character from database, i want auto replace pagetext from database
Thank you very much

--------------- Added [DATE]1391756672[/DATE] at [TIME]1391756672[/TIME] ---------------

Please help me