php中的部分字符串比较

$str1 = "Hello";
$str2 = "World";
$result = strcmp($str1, $str2);
if ($result == 0) {
    echo "The strings are equal.";
} elseif ($result < 0) {
    echo "The string '$str1' is less than the string '$str2'.";
} else {
    echo "The string '$str1' is greater than the string '$str2'.";
}

$str1 = "Hello";
$str2 = "World";
$result = substr_compare($str1, $str2, 0, 3);
if ($result == 0) {
    echo "The first three characters of the strings are equal.";
} elseif ($result < 0) {
    echo "The first three characters of the string '$str1' are less than the first three characters of the string '$str2'.";
} else {
    echo "The first three characters of the string '$str1' are greater than the first three characters of the string '$str2'.";
}