如果用错方法函数或是用少了，如果几个方法函数的逻辑顺序错了，很可能就是一个漏洞，而且不容易找出来。纠结啊~

上网找找看哪位高人有总结出相关的结论出来，果然有！不过似乎不是很全面，我在这里稍完善了一下，仅供参考。复制代码 代码如下:
// 判断 0 与 ""、null、empty、false 之间的关系
$a = 0;
echo "0 与 ""、 empty、null、false 之间的关系：";
if($a == ""){
echo "0 == "";";
}else{
echo "0 != "";";
}
if(trim($a) == ""){
echo "trim(0) == "";";
}else{
echo "trim(0) != "";";
}
if(strval($a) == ""){
echo "strval(0) == "";";
}else{
echo "strval(0) != "";";
}
if($a === ""){
echo "0 === "";";
}else{
echo "0 !=== "";";
}
if(empty($a)){
echo "0 is empty;";
}else{
echo "0 is not empty;";
}
if(is_null($a)){
echo "0 is null;";
}else{
echo "0 is not null;";
}
if(is_numeric($a)){
echo "0 is numeric;";
}else{
echo "0 is not numeric;";
}
if(is_string($a)){
echo "0 is string;";
}else{
echo "0 is not string;";
}
if(!$a){
echo "0 is false;";
}else{
echo "0 is not false;";
}
// 判断 "" 和 0、null、empty、false 之间的关系
$a = "";
echo """ 和 0、empty、null、false 之间的关系：";
if($a == 0){
echo """ == 0;";
}else{
echo """ != 0;";
}
if(intval($a) == 0){
echo "intval("") == 0;";
}else{
echo "intval("") != 0;";
}
if(empty($a)){
echo """ is empty;";
}else{
echo """ is not empty;";
}
if(is_null($a)){
echo """ is null;";
}else{
echo """ is not null;";
}
if(is_numeric($a)){
echo """ is numeric;";
}else{
echo """ is not numeric;";
}
if(is_string($a)){
echo """ is string;";
}else{
echo """ is not string;";
}
if(!$a){
echo """ is false;";
}else{
echo """ is not false;";
}
// 判断 null 和 ""、0、empty、false 之间的关系
$a = null;
echo "null 和 ""、0、empty、false 之间的关系：";
if($a == ""){
echo "null == "";";
}else{
echo "null != "";";
}
if($a == 0){
echo "null == 0;";
}else{
echo "null != 0;";
}
if($a === ""){
echo "null === "";";
}else{
echo "null !=== "";";
}
if($a === 0){
echo "null === 0;";
}else{
echo "null !=== 0;";
}
if(strval($a) == ""){
echo "strval(null) == "";";
}else{
echo "strval(null) != "";";
}
if(intval($a) == 0){
echo "intval(null) == 0;";
}else{
echo "intval(null) != 0;";
}
if(empty($a)){
echo "null is empty;";
}else{
echo "null is not empty;";
}
if(is_numeric($a)){
echo "null is numeric;";
}else{
echo "null is not numeric;";
}
if(is_string($a)){
echo "null is string;";
}else{
echo "null is not string;";
}
if(!$a){
echo "null is false;";
}else{
echo "null is not false;";
}
echo "";
输出的结果是：

我想根据输出结果都可以清楚了解决空字符串、0、null、empty和false之间的大概关系，在开发过程中灵活运用上述代码里的方法，加上良好的逻辑，基本上应该是不会出现问题的了。点击下载相关源代码