How would you create a string of all UTF-8 characters?

Question

There are many ways to represent the +1 million UTF-8 characters. Take the latin capital \"A\" with macron (Ā). This is unicode code point U+0100,

Answer 1

You can leverage iconv (or a few other functions) to convert a code point number to a UTF-8 string:

function unichr($i)
{
    return iconv('UCS-4LE', 'UTF-8', pack('V', $i));
}

$codeunits = array();
for ($i = 0; $i<0xD800; $i++)
    $codeunits[] = unichr($i);
for ($i = 0xE000; $i<0xFFFF; $i++)
    $codeunits[] = unichr($i);
$all = implode($codeunits);

(I avoided the surrogate range 0xD800–0xDFFF as they aren't valid to put in UTF-8 themselves; that would be “CESU-8”.)