php空字符串false,PHP中空字符串介绍0、null、empty和false之间的关系_php技巧

如果用错方法函数或是用少了&＃xff0c;如果几个方法函数的逻辑顺序错了&＃xff0c;很可能就是一个漏洞&＃xff0c;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&＃xff0c;果然有&＃xff01;不过似乎不是很全面&＃xff0c;我在这里稍完善了一下&＃xff0c;仅供参考。

// 判断 0 与 &＃39;&＃39;、null、empty、false 之间的关系

$a &＃61; 0;

echo "0 与 &＃39;&＃39;、 empty、null、false 之间的关系&＃xff1a;";

if($a &＃61;&＃61; &＃39;&＃39;){

echo "0 &＃61;&＃61; &＃39;&＃39;;";

}else{

echo "0 !&＃61; &＃39;&＃39;;";

}

if(trim($a) &＃61;&＃61; &＃39;&＃39;){

echo "trim(0) &＃61;&＃61; &＃39;&＃39;;";

}else{

echo "trim(0) !&＃61; &＃39;&＃39;;";

}

if(strval($a) &＃61;&＃61; &＃39;&＃39;){

echo "strval(0) &＃61;&＃61; &＃39;&＃39;;";

}else{

echo "strval(0) !&＃61; &＃39;&＃39;;";

}

if($a &＃61;&＃61;&＃61; &＃39;&＃39;){

echo "0 &＃61;&＃61;&＃61; &＃39;&＃39;;";

}else{

echo "0 !&＃61;&＃61;&＃61; &＃39;&＃39;;";

}

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 &＃39;&＃39; 和 0、null、empty、false 之间的关系

$a &＃61; &＃39;&＃39;;

echo "&＃39;&＃39; 和 0、empty、null、false 之间的关系&＃xff1a;";

if($a &＃61;&＃61; 0){

echo "&＃39;&＃39; &＃61;&＃61; 0;";

}else{

echo "&＃39;&＃39; !&＃61; 0;";

}

if(intval($a) &＃61;&＃61; 0){

echo "intval(&＃39;&＃39;) &＃61;&＃61; 0;";

}else{

echo "intval(&＃39;&＃39;) !&＃61; 0;";

}

if(empty($a)){

echo "&＃39;&＃39; is empty;";

}else{

echo "&＃39;&＃39; is not empty;";

}

if(is_null($a)){

echo "&＃39;&＃39; is null;";

}else{

echo "&＃39;&＃39; is not null;";

}

if(is_numeric($a)){

echo "&＃39;&＃39; is numeric;";

}else{

echo "&＃39;&＃39; is not numeric;";

}

if(is_string($a)){

echo "&＃39;&＃39; is string;";

}else{

echo "&＃39;&＃39; is not string;";

}

if(!$a){

echo "&＃39;&＃39; is false;";

}else{

echo "&＃39;&＃39; is not false;";

}

// 判断 null 和 &＃39;&＃39;、0、empty、false 之间的关系

$a &＃61; null;

echo "null 和 &＃39;&＃39;、0、empty、false 之间的关系&＃xff1a;";

if($a &＃61;&＃61; &＃39;&＃39;){

echo "null &＃61;&＃61; &＃39;&＃39;;";

}else{

echo "null !&＃61; &＃39;&＃39;;";

}

if($a &＃61;&＃61; 0){

echo "null &＃61;&＃61; 0;";

}else{

echo "null !&＃61; 0;";

}

if($a &＃61;&＃61;&＃61; &＃39;&＃39;){

echo "null &＃61;&＃61;&＃61; &＃39;&＃39;;";

}else{

echo "null !&＃61;&＃61;&＃61; &＃39;&＃39;;";

}

if($a &＃61;&＃61;&＃61; 0){

echo "null &＃61;&＃61;&＃61; 0;";

}else{

echo "null !&＃61;&＃61;&＃61; 0;";

}

if(strval($a) &＃61;&＃61; &＃39;&＃39;){

echo "strval(null) &＃61;&＃61; &＃39;&＃39;;";

}else{

echo "strval(null) !&＃61; &＃39;&＃39;;";

}

if(intval($a) &＃61;&＃61; 0){

echo "intval(null) &＃61;&＃61; 0;";

}else{

echo "intval(null) !&＃61; 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&＃xff1a;

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&＃xff0c;在开发过程中灵活运用上述代码里的方法&＃xff0c;加上良好的逻辑&＃xff0c;基本上应该是不会出现问题的了。

点击下载相关源代码

相关标签&＃xff1a;空字符串

本文原创发布php中文网&＃xff0c;转载请注明出处&＃xff0c;感谢您的尊重&＃xff01;