我如何在PHP中使用或运算符？

Question

if($a=="" and $b=="" or $c=="") {
    echo "something";
}

I want to ask that if $a AND $b is empty then it will print: something. But if $b is not empty, then it will check the statement like this e.g. if $a is empty AND $c is empty then print: something (Means $a is compulsory to check with the variable which is empty $b OR $c)

Answer 1

Just force the comparison order/precedence by using parentheses:

if( $a == "" and ( $b == "" or $c == "" ) )

But you would be better off using && and ||:

if( $a == "" && ( $b == "" || $c == "" ) )