Find first character that is different between two strings

Question

Given two equal-length strings, is there an elegant way to get the offset of the first different character?

The obvious solution would be:

for ($offs         


        

Answer 1

If you convert a string to an array of single character one byte values you can use the array comparison functions to compare the strings.

You can achieve a similar result to the XOR method with the following.

$string1 = 'foobarbaz';
$string2 = 'foobarbiz';

$array1 = str_split($string1);
$array2 = str_split($string2);

$result = array_diff_assoc($array1, $array2);

$num_diff = count($result);
$first_diff = key($result);

echo "There are " . $num_diff . " differences between the two strings. 
";
echo "The first difference between the strings is at position " . $first_diff . ". (Zero Index) '$string1[$first_diff]' vs '$string2[$first_diff]'.";

Edit: Multibyte Solution

$string1 = 'foorbarbaz';
$string2 = 'foobarbiz';

$array1 = preg_split('((.))u', $string1, PREG_SPLIT_DELIM_CAPTURE | PREG_SPLIT_NO_EMPTY);
$array2 = preg_split('((.))u', $string2, PREG_SPLIT_DELIM_CAPTURE | PREG_SPLIT_NO_EMPTY);

$result = array_diff_assoc($array1, $array2);

$num_diff = count($result);
$first_diff = key($result);

echo "There are " . $num_diff . " differences between the two strings.\n";
echo "The first difference between the strings is at position " . $first_diff . ". (Zero Index) '$string1[$first_diff]' vs '$string2[$first_diff]'.\n";