如何用值来检查php中的空变量？

Question

I have a string:

$string

if I print it nothing return to me:

echo $string; // result in browser: blank!  in html source code:&nbsp

I try use this code to undererstand $string is empty!

if ($string!= '&nbsp' && $string!= ' ' && $string!= '' && $string!= null && $string!= '  ' && !empty($string))
echo 'true';
else
echo 'false';

But It always return me 'true', why? //I think in $string there many space or sth like that

Answer 1

I checked it, this should work:

$strings = ['', ' ', ' ', 's', 's ', ' s'];

foreach ($strings as $string)
{
    $string = trim(str_replace(' ', ' ', $string));

    if (strlen($string) != 0)
        echo $string . ' is not empty';
    else
        echo $string . ' is empty';

    echo '<br>';
}

Output:

is empty
is empty
is empty
s is not empty
s is not empty
s is not empty