Description:
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I have a variable called $config['sold_email_winner_message'], which has an emal message template stored in the variable.  Within this email message, i have information like:

Dear $winner_info[first_name] $winner_info[last_name],

Congrates...

I use eval to evaluate the string.  One thing I noticed is that the following doesn't work

$winner_info['first_name'] $winner_info['last_name'], but $winner_info[first_name] $winner_info[last_name] does work.

One would think that these should be interchangeable.

Reproduce code:
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$winner_info = array ('first_name' => "First", 'last_name' => "Last");

This doesn't work:

$config['sold_email_winner_message'] = "Dear $winner_info['first_name'] $winner_info['last_name']";
eval ("\$config[sold_email_winner_message] = \"$config[sold_email_winner_message]\";");

This does work:
$config['sold_email_winner_message'] = "Dear $winner_info[first_name] $winner_info[last_name]";
eval ("\$config[sold_email_winner_message] = \"$config[sold_email_winner_message]\";");

Expected result:
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This will print the following:
Dear First Last

Actual result:
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This will print the following:
Dear $winner_info['first_name'] $winner_info['last_name']