I know that strings in php are ..... strings but for example I can do
$str = \'String\';
echo $str[0];
echo $str[1];
//result
S
t
echo count($str)
//result
Because strings are not arrays. They allow you to find letters byte offsets (which aren't necessarily letters in a multi-byte character string) using the same syntax for your convenience, but that's about it.
Arrays can have keys as well and can be sorted. If strings were full arrays, you could give each letter a key, or sort the letters alphabetically using one of the array functions.
Long story short: a string is not an array, even when a tiny part of their syntax is similar.