What do commas mean in a variable declaration?

问题

I've found this in includes/parser/Parser.php of MediaWiki PHP source:

public function replaceInternalLinks2( &$s ) {
    global $wgExtraInterlanguageLinkPrefixes;
    static $tc = false, $e1, $e1_img;
    //...
}

What is this comma delimited list? What value $tc receives?

回答1:

It's the same as:

static $tc = false;
static $e1;
static $e1_img;

So $tc received false.

来源：https://stackoverflow.com/questions/41383218/what-do-commas-mean-in-a-variable-declaration