#php non obvious behavior of nested ternary

nested-ternary.php

<?php 

$arg = 'T';
$vehicle = ( $arg == 'B' ) ? 'bus' :
           ( $arg == 'A' ) ? 'airplane' :
           ( $arg == 'T' ) ? 'train' :
           ( $arg == 'C' ) ? 'car' :
           ( $arg == 'H' ) ? 'horse' :
           'feet';
echo $vehicle; 

//will echo horse not train

$arg = 'T';
$vehicle = (( ( $arg == 'B' ) ? 'bus' :
           (( $arg == 'A' ) ? 'airplane' :
           (( $arg == 'T' ) ? 'train' :
           (( $arg == 'C' ) ? 'car' :
           (( $arg == 'H' ) ? 'horse' :
           'feet' ))))));
echo $vehicle; 

//will echo train

//http://17thdegree.com/archives/2008/01/09/php-and-nesting-ternary-operators/
//http://www.php.net/manual/en/language.operators.comparison.php#example-138    

/* explanation
$test = 'one';
echo $test == 'one' ? 'one' :  $test == 'two' ? 'two' : 'three';

What PHP will do is evaluate this the first ternary section and return a value, 
in this case it is the string ‘one’. 
The boolean value of the string ‘one’ is true. So, for the second ternary operation, ‘two’ gets selected.
The way a nested ternary operator is evaluated in PHP is left to right. (Probably no other languages acts like this.)
*/