PHP mb_convert_encoding string encoding

1 introduces the  
mb_convert_encoding ($str, $encoding 1, $encoding 2)  
$str, to convert the encoded string  
$encoding 1, the target encoding, such as UTF-8,GBK, The case can be  
$encoding 2, the original encoding, such as UTF-8,GBK, case can be  
2 instances 1  
<?php
$str = ' coding ';  
Echo mb_convert_encoding ($str, "UTF-8"); Code conversion to Utf-8  
?>  
3 instance 2  
<?php
$str = ' encoding ';  
Echo mb_convert_encoding ($str, "UTF-8", "GBK"); Known original encoding as GBK, converted to Utf-8  
?>  
4 instance 3  
<?php
$str = ' encoding ';  
Echo mb_convert_encoding ($str, "UTF-8", "Auto"); Unknown original code, auto automatic detection, conversion code for UTF-8  
?>