(PECL ds >= 1.0.0)
Ds\Stack::peek — Returns the value at the top of the stack.
Returns the value at the top of the stack, but does not remove it.
此函数没有参数。
The value at the top of the stack.
UnderflowException if empty.
Example #1 Ds\Stack::peek() example
<?php
$stack = new \Ds\Stack();
$stack->push("a");
$stack->push("b");
$stack->push("c");
var_dump($stack->peek());
?>
以上例程的输出类似于：
string(1) "c"