php把一个字符串分割成字符数组（可以用参数指定数组每个元素字符的长度）

function str_split_unicode($str, $l = 0) {
    if ($l > 0) {
        $ret = array();
        $len = mb_strlen($str, "UTF-8");
        for ($i = 0; $i < $len; $i += $l) {
            $ret[] = mb_substr($str, $i, $l, "UTF-8");
        }
        return $ret;
    }
    return preg_split("//u", $str, -1, PREG_SPLIT_NO_EMPTY);
}

例子：

$s = 'abc你好吗defgh';
$strArr = str_split_unicode($s);
print_r($strArr);

输出：Array ( [0] => a [1] => b [2] => c [3] => 你 [4] => 好 [5] => 吗 [6] => d [7] => e [8] => f [9] => g [10] => h )

例子2：

$s = 'abc你好吗defgh'; 
$strArr = str_split_unicode($s,3);
print_r($strArr);

输出：Array ( [0] => abc [1] => 你好吗 [2] => def [3] => gh )