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

If you use the wrong method function or use it too little, or if the logical order of several method functions is wrong, it is likely to be a loophole, and it is not easy to find out. So confused~

Look online to see if any expert has come up with relevant conclusions, and sure enough, there is! But it doesn’t seem to be very comprehensive. I have improved it a little here for reference only.

Copy code The code is as follows:

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

The output 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 problems.

Click to download the relevant source code

http://www.bkjia.com/PHPjc/325931.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/325931.htmlTechArticleIf you use the wrong method function or use too little, if the logical order of several method functions is wrong, it is very likely that It's just a loophole, and it's not easy to find. I’m so confused~ Let’s look online to see which one is taller...