PHP defines the array using commas,

One . Preface

In the process of looking at the code , Found a strange code , And Baidu hasn't come out yet... What's the use , So here's a record of .
Code up ：

 if (in_array($test, [1,])) {
        }
        //  This  [1,]

Two . Test it

$test_id = 10;
$arr = [1,];
if(in_array($test_id,$arr)){
print_r("yes");
}
print_r($arr);
//====================
 result ：
Array
(
    [0] => 1
)

in other words , This gadget is equivalent to an ordinary definition array [1], I didn't find anything else special ... If a big man sees and just knows this , I hope you can give me some advice

end