PHP empty string describes the relationship between 0, null, empty, and false

: This article mainly introduces the relationship between 0, null, empty, and false in PHP empty strings. For more information about PHP tutorials, see. // Determine the relationship between 0 and '', null, empty, and false
$ A = 0;
Echo "relationship between 0 and'', empty, null, and 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 ($ )){
Echo "0 is empty ;";
} Else {
Echo "0 is not empty ;";
}
If (is_null ($ )){
Echo "0 is null ;";
} Else {
Echo "0 is not null ;";
}
If (is_numeric ($ )){
Echo "0 is numeric ;";
} Else {
Echo "0 is not numeric ;";
}
If (is_string ($ )){
Echo "0 is string ;";
} Else {
Echo "0 is not string ;";
}
If (! $ ){
Echo "0 is false ;";
} Else {
Echo "0 is not false ;";
}
// Judge the relationship between ''and 0, null, empty, and false.
$ A = '';
Echo "the relationship between'' and 0, empty, null, and false :";
If ($ a = 0 ){
Echo "'' = 0 ;";
} Else {
Echo "''! = 0 ;";
}
If (intval ($ a) = 0 ){
Echo "intval ('') = 0 ;";
} Else {
Echo "intval ('')! = 0 ;";
}
If (empty ($ )){
Echo "'' is empty ;";
} Else {
Echo "'' is not empty ;";
}
If (is_null ($ )){
Echo "'' is null ;";
} Else {
Echo "'' is not null ;";
}
If (is_numeric ($ )){
Echo "'' is numeric ;";
} Else {
Echo "'' is not numeric ;";
}
If (is_string ($ )){
Echo "'' is string ;";
} Else {
Echo "'' is not string ;";
}
If (! $ ){
Echo "'' is false ;";
} Else {
Echo "'' is not false ;";
}
// Determine the relationship between null and '', 0, empty, and false
$ A = null;
Echo "relationship between null and'', 0, empty, and 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 ($ )){
Echo "null is empty ;";
} Else {
Echo "null is not empty ;";
}
If (is_numeric ($ )){
Echo "null is numeric ;";
} Else {
Echo "null is not numeric ;";
}
If (is_string ($ )){
Echo "null is string ;";
} Else {
Echo "null is not string ;";
}
If (! $ ){
Echo "null is false ;";
} Else {
Echo "null is not false ;";
}
Echo "";

The output result is:

Based on the output results, I want to clearly understand the approximate relationship between null strings, 0, null, empty, and false, and flexibly use the methods in the above code during development, with good logic, there should be no problems.

The above introduces the relationship between 0, null, empty, and false in PHP hollow strings, including some content, and hope to help those who are interested in PHP tutorials.