<?php
/**
 * Created by PhpStorm.
 */

//php7新特性，组合运算符, $a <=> $b ,当a大于b时，返回 1，a等于b时，返回0，a小于b时，返回-1.
echo 1 <=> 1;  // 返回0
echo 1 <=> 2;  // 返回-1
echo 2 <=> 1;  // 返回1

echo 5.5 <=> 5.5;  //return 0
echo 5.5 <=> 7.0;  // return -1
echo 7.0 <=> 5.5;  // return 1

echo "a" <=> "a";  // return 0
echo "a" <=> "b";  // return -1
echo "b" <=> "a";  // return 1