An array problem with PHP

Recently in doing a project, I found that in PHP, if you want to assign a value to an element of a data, you will get an error:

? PHP
$str = " 222222 " ;
$var = Array (
A => " 1 " ,
b => $str ,
C => ""
);
if ( $var [b]) {
$var [C] = $var [b];
}
?>  
An error is prompted, indicating that no constants are defined.
There are two ways to solve this situation, one is to change the configuration of php.ini
Modify the php.ini to change the error_reporting = E_all
error_reporting = E_all & ~e_notice
If this doesn't work out,
Just put

Replace into

<