php"><?php
if('safdasefasefasf'==0){
 echo "该字符串转换为数字  等于 0 <br/>";
} //output:该字符串转换为数字 等于零。
?>

<?php
$a=0;
if($a==''){
 echo "0  等于  '' <br/>";
}    //output:0 等于''

if(trim($a)==''){
 echo "trim(0)等于'' <br/>";
}    //no output
  
if($a===''){
 echo "0==='' <br/>";
}    //no output

if(empty($a)){
 echo "'' is empty <br/>";
}   //output:'' is empty

if(is_null($a)){
 echo "0 is null <br/>";
}   //no output

if(is_numeric($a)){
 echo "0 is numeric <br/>";
}   //output:0 is numeric

if(is_string($a)){
 echo "0 is string <br/>";
}   //no output

if(strval($a)==''){
 echo "转换成字符串的0 is '' <br/>";
}   //no output

$b = '';
if($b==0){
 echo "''  等于  0 <br/>";
}    //output:''  等于  0

if(!''){
 echo "'' 就是false <br/>";
}    //output:'' 就是false

if(!0){
 echo "0 就是false <br/>";
}    //output:0 就是false


echo         0 == null;
//true
echo         0 === null;
//false
echo (string)0 != null;
//true
echo         0 != null;
//false
echo         0 !== null;
//true

?>