基于empty函数的输出详解

$a = "";
echo "1.---------------".empty（$a）." ";
$a = "0";
echo "2.---------------".empty（$a）." ";
$a = 0;
echo "3.---------------".empty（$a）." ";
$a = null;
echo "4.---------------".empty（$a）." ";
$a = "null";
echo "5.---------------".empty（$a）." ";
$a = "abc";
echo "6.---------------".empty（$a）." ";
$a = true;
echo "7.---------------".empty（$a）." ";
$a = "true";
echo "8.---------------".empty（$a）." ";
$a = false;
echo "9.---------------".empty（$a）." ";
$a = "false";
echo "10.---------------".empty（$a）." ";
$a = 1;
echo "11.---------------".empty（$a）." ";
$a = "1";
echo "12.---------------".empty（$a）." ";
$a = "null";
echo "13.---------------".！empty（$a）." ";
结果：
1.---------------1
2.---------------1
3.---------------1
4.---------------1
5.---------------
6.---------------
7.---------------
8.---------------
9.---------------1
10.---------------
11.---------------
12.---------------
13.---------------1