问一个Js的语法,在PHP该怎样表示?解决方法

问一个Js的语法,在PHP该怎样表示?
Javascript:

JScript code

<!--Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/-->var a = 'a';var b = null;alert(a||b);//这会输出a的变量值,,想问一下php应该怎么表示?

PHP code

<!--Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/-->$a = 'A';$b = null;echo $a || $b;//这样只会输出1或0,,//我以前记得在哪个Oauth的开发文档上看过...但我现在忘记了...//不知道有能人能告诉一下本人..Thanks

------解决方案--------------------
$a = 'A';
$b = null;
$c = $a or $c = $b;
echo $c;