How to remove array elements that are containing only white spaces? [duplicate]

This question already has an answer here:

• How do you strip whitespace from an array using PHP? 3 answers

I have an array like this:

$arr = array (0 => 'red',
              1 => '   ',
              2 => 'blue',
              3 => '       ',
              4 => 'green',
              5 => '  ',
              6 => 'white',
              7 => '    ',
              8 => 'black',
              9 => '           ' );

Well I'm trying to remove all items which are just containing white space(s). So this it expected result:

$arr = array (0 => 'red',
              1 => 'blue',
              2 => 'green',
              3 => 'white',
              4 => 'black');

I can do that if those white spaces item be empty. So I can use $arr = array_filter($arr);. But in this case, because there is white spaces instead of nothing, array_filter() isn't useful. Is there any approach to do that?