php中值的真真假假

你是否還模糊？？？

<?php
$arr = ["a" => null, "b" => "","c" => 0];
echo "array_key_exists,值爲 null 爲:";
var_export(array_key_exists("a", $arr));
echo "\nisset 值爲 null 時，判斷爲:";
var_export(isset($arr["a"]));
echo "\nisset 空字符串時返回:";
var_export(isset($arr["b"]));
echo "\n isset 0 時返回:";
var_export(isset($arr["c"]));
echo "\nempty null 返回：";
var_export(empty($arr["a"]));
echo "\nempty 空字符串 返回：";
var_export(empty($arr["b"]));
echo "\nempty 0 返回：";
var_export(empty($arr["c"]));
echo "\n";
echo $arr["a"] ? "null value is true":"null value is false";
echo "\n";
echo $arr["b"] ? "空字符串 is true":"空字符串 is false";
echo "\n";
echo $arr["c"] ? "0 is true":"0 is false";
?>