PHP变量解析

$fruits = array('strawberry' => 'red', 'banana' => 'yellow');
// Works but note that this works differently outside string-quotes
echo "A banana is $fruits[banana].";
// Works
echo "A banana is {$fruits['banana']}.";

// Works but PHP looks for a constant named banana first
// as described below.
echo "A banana is {$fruits[banana]}.";

// Works
echo "A banana is " . $fruits['banana'] . ".";
?>

输出:
A banana is yellow.A banana is yellow.A banana is red.A banana is yellow.