php中$i++与++$i的区别

代码

        $i = 1;
        $a = $i++; // 先赋值,再自增。等价于$a = $i; $i = $i + 1
        echo "i = ".$i;
        echo "a = ".$a;

        $j = 1;
        $b = ++$j; // 先自增,再赋值。等价于$j = $j + 1; $b = $j 
        echo "j = ".$j;
        echo "b = ".$b;

输出

i = 2
a = 1
j = 2
b = 2