问题
Hope u people will be fine. I’m working on a following code in which i want to use multiple php if conditions with multiple not operators (example is below), but when i execute following php code, it always returns true (mean content in always parenthesis always executed) even no condition is true. I want to ask what is the problem in following code. Is there any specific syntax or rule for using multiple != operator in php conditions. And i am amazed to see that if i use following code by replacing != operator with == operator it is working fine.
if( $ext!="exe" || $ext!="html" || $ext!="htm" || $ext!="js" || $ext!="iso" || $ext!="zip" || $ext!="rar" )
{ // ececk extension
echo $ext."extension";
}
else{
echo "not match";
}
Waiting for your kind replies. and sorry for my bad english.
回答1:
Better code:
$allowed = array('jpeg','png');
if(in_array($ext,$allowed)){
echo "Correct";
}
else {
echo "Wrong";
}
回答2:
User XOR operator instead of OR as or checked all condition need to be identical while XOR return true if anyone from all is identical:
if(!($ext!=="exe") xor ($ext=="html")){ //Add more conditions
//each condition in new brackets & ! sign in start before all conditions
{ // ececk extension
echo $ext."extension";
}
else{
echo "not match";
}
Hope it will help
来源：https://stackoverflow.com/questions/16249373/php-multiple-conditions-with-not-equal-operator-is-not-working