为什么$ string [0] =''不会导致$ string [0] ===''？

Question

$s = 'abc';
$s[0] = '';
if ($s[0] !== '') {
    echo 'emmm';
}

Why $string[0] = '' is not resulting $string[0] === ''?

seems like $string[0] === "\0", but more confusing..

Answer 1

$s[0] gives access to a single character of the string. '' is not a character, it's a string, so the assignment fails. You get the exact same behavior if you try to assign FALSE to $s[0]. It looks like PHP does its best to convert whatever value you assign into a single character. If you assign a non-empty string, it will use the first character. If you assign a number, it will use the first digit. If you assign the value TRUE, it will use 1.