why do I need mb_convert_encoding to show the correct characters

my website have charset=UTF-8, and mysql DATABASE is also set to be UTF-8 encoding.

my problem is that when I retrieve text from mysql to the website, i need to use php function mb_convert_encoding(@db_field,'utf-8','iso-8859-1') to show the text properly. it looks like that system think mysql DB is in iso-8859-1.

Run this right after you connect to the database:

mysqli_query("SET NAMES utf8"); /* or mysql_query */

It is not enough to set the collation of the table to UTF-8, you also need to specify (with this query) the encoding that should be used during the communication between PHP and the MySQL server.
More details here: SET NAMES utf8 in MySQL?

Ensuring UTF-8 compatibility everywhere is tricky; my UTF-8 checklist is as follows:

• Make sure every source file is saved as UTF-8
• Ensure <meta charset="UTF-8" /> is present on all pages
• Make sure every database table is set to use UTF-8
• Run SET NAMES utf8 after connecting to the database
• Call mb_internal_encoding("UTF-8") at the beginning of the script and use mb_ string functions where possible