php eval()函数用法

<?php
$string = "beautiful";
$time = "winter";

$str = 'This is a $string $time morning!';
echo $str. "<br />";

eval("\$str = \"$str\";");
echo $str;
?>

<?php
$str = "array('a'=>'123','b'=>'456')";
eval("\$arr= ".$str.";");
var_dump($arr);