PHP function to replace a (i)th-position character

Question

Is there a function in PHP that takes in a string, a number (i), and a character (x), then replaces the character at position (i) with

Answer 1

$str    = 'bar';
$str[1] = 'A';
echo $str; // prints bAr

or you could use the library function substr_replace as:

$str = substr_replace($str,$char,$pos,1);