从4.0.6版开始，PHP就内置了这个功能。去看医生。

echo mb_strimwidth('Hello World', 0, 10, '...');

// outputs Hello W...

注意trimmarker(上面的省略号)包含在截断的长度中。

最好像这样抽象你的代码(注意限制是可选的，默认为10):

print limit($string);


function limit($var, $limit=10)
{
    if ( strlen($var) > $limit )
    {
        return substr($string, 0, $limit) . '...';
    }
    else
    {
        return $var;
    }
}

$yourString = "bla blaaa bla blllla bla bla";
$out = "";
if(strlen($yourString) > 22) {
    while(strlen($yourString) > 22) {
        $pos = strrpos($yourString, " ");
        if($pos !== false && $pos <= 22) {
            $out = substr($yourString,0,$pos);
            break;
        } else {
            $yourString = substr($yourString,0,$pos);
            continue;
        }
    }
} else {
    $out = $yourString;
}
echo "Output String: ".$out;

如果对截断字符串的长度没有硬性要求，可以使用这个来截断并防止截断最后一个单词:

$text = "Knowledge is a natural right of every human being of which no one
has the right to deprive him or her under any pretext, except in a case where a
person does something which deprives him or her of that right. It is mere
stupidity to leave its benefits to certain individuals and teams who monopolize
these while the masses provide the facilities and pay the expenses for the
establishment of public sports.";

// we don't want new lines in our preview
$text_only_spaces = preg_replace('/\s+/', ' ', $text);

// truncates the text
$text_truncated = mb_substr($text_only_spaces, 0, mb_strpos($text_only_spaces, " ", 50));

// prevents last word truncation
$preview = trim(mb_substr($text_truncated, 0, mb_strrpos($text_truncated, " ")));

在本例中，$preview将是“Knowledge is a natural right of every human”。

动态代码示例: http://sandbox.onlinephpfunctions.com/code/25484a8b687d1f5ad93f62082b6379662a6b4713

要在函数内创建(用于重复使用)并动态限制长度，请使用:

function string_length_cutoff($string, $limit, $subtext = '...')
{
    return (strlen($string) > $limit) ? substr($string, 0, ($limit-strlen(subtext))).$subtext : $string;
}

// example usage:
echo string_length_cutoff('Michelle Lee Hammontree-Garcia', 26);

// or (for custom substitution text
echo string_length_cutoff('Michelle Lee Hammontree-Garcia', 26, '..');

如果你想要切割，小心不要分割单词，你可以做下面的事情

function ellipse($str,$n_chars,$crop_str=' [...]')
{
    $buff=strip_tags($str);
    if(strlen($buff) > $n_chars)
    {
        $cut_index=strpos($buff,' ',$n_chars);
        $buff=substr($buff,0,($cut_index===false? $n_chars: $cut_index+1)).$crop_str;
    }
    return $buff;
}

如果$str比$n_chars短，则原形返回。

如果$str等于$n_chars也会返回它。

如果$str比$n_chars长，那么它会寻找下一个空格来切割，或者(如果直到最后没有更多的空格)$str会在$n_chars被粗鲁地切割。

注意:注意此方法将删除HTML中的所有标记。