PHP hollow string introduces the relationship between 0, null, empty and false

// Determine the relationship between 0 and '', null, empty, false
$a = 0;
echo "The relationship between 0 and '', empty, null, false: ";
if($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;";
}
//Judge' ' The relationship between 0, null, empty, false
$a = '';
echo The relationship between "'' and 0, empty, null, false: ";
if($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;";
}
// Determine the relationship between null and '', 0, empty, false
$a = null;
echo "The relationship between null and '', 0, empty, false: ";
if($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 "";

output The result is:

I think based on the output results, I can clearly solve the rough relationship between empty strings, 0, null, empty and false. During the development process, I can flexibly use the methods in the above code and add good logic. Basically There should be no problem.

The above has introduced the relationship between 0, null, empty and false in PHP hollow strings, including aspects of the content. I hope it will be helpful to friends who are interested in PHP tutorials.