为什么变量与数学运算不起作用？ [关闭]

Question

I have a predefined array $ar .

$num = count($ar) - 2;
print $ar[$num];

I always get an error when I'm trying to do an opertaion like this. I have also tried

print $ar[count($ar) - 2];

It gives me the same error yet again. I'm just frustrated.Tried so many ways.None of them work. How do i use mathematical symbols???!!

Thanks, Sai

EDIT:

Here is the code.

$linez = "http://directurl.com/image1.png
http://directurl.com/image2.png
";
$ar = explode("
",$linez);
$num = count($ar) - 1;
print $num;

It prints 2 instead of 1

Answer 1

According your edited question : You had a extra new line after two image url in $linez. Your array length is 3 so you got 2 in $num.After removing last newline from $linez your array length is 1=2 so you get 1 in $num

  $linez = "http://directurl.com/image1.png
    http://directurl.com/image2.png";
    $ar = explode("
",$linez);
    $num = count($ar) - 1;
    print $num;

It will work :) Demo : https://eval.in/82417