PHP中如何编写一个通用的字符串截取函数？

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python/*** 提取字符串* @param string 要处理的字符串* @param length 要保留的长度（字符数）* @param dot 超出部分显示的文字* @return 截取后的字符串*/function cutstr($string, $length, $dot='...') { if (strlen($string)==$length) { return $string; } $string=str_replace(array(' ', '　'), '', $string); $length=intval($length); $dotLength=strlen($dot); if ($length <=$dotLength) { return $string . $dot; } $stringLength=strlen($string); $string=str_replace(array(\r, \n, \t, ), '', $string); if ($stringLength <=$length) { return $string; } $string=substr($string, 0, $length - $dotLength) . $dot; return $string;}

/** * 截取字符串 * params $string 要截取的字符串 * params $length: 保留长度（字符数） * params $dot: 多余部分显示 **/ function _cutstr($string, $length, $dot = ' ...') { if(strlen($string) <= $length) { return $string; } $string = str_replace(array('&', '"', '<', '>'), array('&', '"', '<', '>'), $string); $strcut = ''; $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); $strcut = str_replace(array('&', '"', '<', '>'), array('&', '"', '<', '>'), $strcut); return $strcut.$dot; }