PHP 字符串截取和获取字符串长度函数封装

 
/**
 * 字符串截取和返回字符串的长度
 * @param string $str 要截取的字符串
 * @param int $start 字符串截取的初始位置，从0开始
 * @param int $length 字符串截取的长度
 * @param string $charset 字符串编码
 * @param bool $suffix 是否添加后缀
 * @param bool $strlen 是否返回字符串的长度(false不返回,true返回)
 * @return int|string
 */
function my_substr($str, $start = 0, $length, $charset = 'utf-8', $suffix = true, $strlen = false)
{
    $charset || ($charset = 'utf-8');
    //正则表达式匹配编码
    $re['utf-8'] = "/[\x01-\x7f]|[\xc2-\xdf][\x80-\xbf]|[\xe0-\xef][\x80-\xbf]{2}|[\xf0-\xff][\x80-\xbf]{3}/";
    $re['gb2312'] = "/[\x01-\x7f]|[\xb0-\xf7][\xa0-\xfe]/";
    $re['gbk'] = "/[\x01-\x7f]|[\x81-\xfe][\x40-\xfe]/";
    $re['big5'] = "/[\x01-\x7f]|[\x81-\xfe]([\x40-\x7e]|\xa1-\xfe])/";
    //返回字符串长度
    if ($strlen) {
        if (function_exists('mb_strlen')) {
            $count = mb_strlen($str, $charset);
        } elseif (function_exists('iconv_strlen')) {
            $count = iconv_strlen($str, $charset);
        } else {
            preg_match_all($re[$charset], $str, $match);
            $count = count($match[0]);
        }
        return $count;
    }
    //截取字符串
    if (function_exists("mb_substr"))
        $slice = mb_substr($str, $start, $length, $charset);
    elseif (function_exists('iconv_substr')) {
        $slice = iconv_substr($str, $start, $length, $charset);
        if (false === $slice) {
            $slice = '';
        }
    } else {
        preg_match_all($re[$charset], $str, $match);
        $slice = join("", array_slice($match[0], $start, $length));
    }
    //字数不满添加后缀 ...
    if ($suffix) {
        $count = my_substr($str, $start, $length, $charset, false, true);
        if ($count > $length) {
            return $slice . '......';
        } else {
            return $slice;
        }
    } else {
        return $slice;
    }
}

/**
 * 返回字符串长度
 * @param string $str
 * @param string $charset
 * @return int
 */
function my_strlen($str, $charset = 'utf-8')
{
    $charset || ($charset = 'utf-8');
    //正则表达式匹配编码
    $re['utf-8'] = "/[\x01-\x7f]|[\xc2-\xdf][\x80-\xbf]|[\xe0-\xef][\x80-\xbf]{2}|[\xf0-\xff][\x80-\xbf]{3}/";
    $re['gb2312'] = "/[\x01-\x7f]|[\xb0-\xf7][\xa0-\xfe]/";
    $re['gbk'] = "/[\x01-\x7f]|[\x81-\xfe][\x40-\xfe]/";
    $re['big5'] = "/[\x01-\x7f]|[\x81-\xfe]([\x40-\x7e]|\xa1-\xfe])/";

    //返回字符串长度
    if (function_exists('mb_strlen')) {
        $count = mb_strlen($str, $charset);
    } elseif (function_exists('iconv_strlen')) {
        $count = iconv_strlen($str, $charset);
    } else {
        preg_match_all($re[$charset], $str, $match);
        $count = count($match[0]);
    }
    return $count;
}

/**
 * 字符串分隔
 * @param string $str
 * @param int $split_length
 * @param string $charset
 * @return array|array[]|bool|false|string[]
 */
function my_str_split($str, $split_length = 1, $charset = 'utf-8')
{
    if (func_num_args() == 1 && strtolower($charset) === 'utf-8') {
        return preg_split('/(?<!^)(?!$)/u', $str);
    }
    if ($split_length < 1) {
        return false;
    }
    $len = my_strlen($str, $charset);
    $arr = array();
    for ($i = 0; $i < $len; $i += $split_length) {
        $s = my_substr($str, $i, $split_length, $charset, false);
        $arr[] = $s;
    }
    return $arr;
}