php截取字符串函数分享

经常看到有新手问PHP有没有类似asp的left函数或right函数，实现截取某字符串左边或右边开始N个字符的函数。答案当然是有的。PHP中的substr函数就可以做的到，只不过PHP把二个函数合二为一了，这里再给大家分享一个更加优秀的截取字符串的函数。

/**

     * 方法库-截取字符串-【该函数作者未知】

     * @param string  $string 字符串  

     * @param int     $length 字符长度

     * @param string  $dot    截取后是否添加...

     * @param string  $charset编码

     * @return string

     */

    public function cutstr($string, $length, $dot = ' ...', $charset = 'utf-8') {

        if (strlen($string) <= $length) {

            return $string;

        }

        $string = str_replace(array('&', '"', '<', '>'), array('&', '"', '<', '>'), $string);

        $strcut = '';

        if (strtolower($charset) == 'utf-8') {

            $n = $tn = $noc = 0;

            while ($n < strlen($string)) {

                $t = ord($string[$n]);                //ASCIIֵ

                if($t == 9 || $t == 10 || (32 <= $t && $t <= 126)) {

                    $tn = 1; $n++; $noc++;

                } elseif (194 <= $t && $t <= 223) {

                    $tn = 2; $n += 2; $noc += 2;

                } elseif (224 <= $t && $t < 239) {

                    $tn = 3; $n += 3; $noc += 2;

                } elseif (240 <= $t && $t <= 247) {

                    $tn = 4; $n += 4; $noc += 2;

                } elseif (248 <= $t && $t <= 251) {

                    $tn = 5; $n += 5; $noc += 2;

                } elseif ($t == 252 || $t == 253) {

                    $tn = 6; $n += 6; $noc += 2;

                } else {

                    $n++;

                }

                if($noc >= $length) {

                    break;

                }

            }

            if ($noc > $length) {

                $n -= $tn;

            }

            $strcut = substr($string, 0, $n);

        } else {

            for ($i = 0; $i < $length; $i++) {

                $strcut .= ord($string[$i]) > 127 ? $string[$i].$string[++$i] : $string[$i];

            }

        }

        $strcut = str_replace(array('&', '"', '<', '>'), array('&', '"', '<', '>'), $strcut);

        return $strcut.$dot;

    }

以上就是本文的全部内容，希望大家能够喜欢。