PHP substr but keep HTML tags?

Question

I am wondering if there is an elegant way to trim some text but while being HTML tag aware?

For example, I have this string:

$data = '<strong>some title text here that could get very long</strong>';

And let's say I need to return/output this string on a page but would like it to be no more than X characters. Let's say 35 for this example.

Then I use:

$output = substr($data,0,20);

But now I end up with:

<strong>some title text here that 

which as you can see the closing strong tags are discarded thus breaking the HTML display.

Is there a way around this? Also note that it is possible to have multiple tags in the string for example:

<p>some text here <strong>and here</strong></p>

Answer 1

A few mounths ago I created a special function which is solution for your problem.

Here is a function:

function substr_close_tags($code, $limit = 300)
{
    if ( strlen($code) <= $limit )
    {
        return $code;
    }

    $html = substr($code, 0, $limit);
    preg_match_all ( "#<([a-zA-Z]+)#", $html, $result );

    foreach($result[1] AS $key => $value)
    {
        if ( strtolower($value) == 'br' )
        {
            unset($result[1][$key]);
        }
    }
    $openedtags = $result[1];

    preg_match_all ( "#</([a-zA-Z]+)>#iU", $html, $result );
    $closedtags = $result[1];

    foreach($closedtags AS $key => $value)
    {
        if ( ($k = array_search($value, $openedtags)) === FALSE )
        {
            continue;
        }
        else
        {
            unset($openedtags[$k]);
        }
    }

    if ( empty($openedtags) )
    {
        if ( strpos($code, ' ', $limit) == $limit )
        {
            return $html."...";
        }
        else
        {
            return substr($code, 0, strpos($code, ' ', $limit))."...";
        }
    }

    $position = 0;
    $close_tag = '';
    foreach($openedtags AS $key => $value)
    {   
        $p = strpos($code, ('</'.$value.'>'), $limit);

        if ( $p === FALSE )
        {
            $code .= ('</'.$value.'>');
        }
        else if ( $p > $position )
        {
            $close_tag = '</'.$value.'>';
            $position = $p;
        }
    }

    if ( $position == 0 )
    {
        return $code;
    }

    return substr($code, 0, $position).$close_tag."...";
}

Here is DEMO: http://sandbox.onlinephpfunctions.com/code/899d8137c15596a8528c871543eb005984ec0201 (click "Execute code" to check how it works).