php源码分析之DZX1.5字符串截断函数cutstr用法

<?php 
/**
 * 函数来源DZX1.5，文件所在 /source/function/function_core.php
 */
define('CHARSET','UTF-8');
function cutstr($string, $length, $dot="...") {
  if(strlen($string)<=$length) {
    return $string;
  }
  if(strtolower(CHARSET) == "utf-8") {
    $n = $tn = $noc = 0;
    while($n < strlen($string)) {
      $t = ord($string[$n]);
      if($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];
    }
  }
  $pos = strrpos($strcut, chr(1));
  if($pos !== false) {
    $strcut = substr($strcut,0,$pos);
  }
  return $strcut.$dot;
}
$string = '测试数据库ablci102020@(#)!)!测试劳动力ddk';
echo cutstr($string,15);
/*End of php*/