php - GetBetween for multiple findings?

Question

I have a working getbetween function which finds the value between 2 tags.

function GetBetween($content,$start,$end){
    $r = explode($start, $content);
    if (isset($r[1])){
        $r = explode($end, $r[1]);
        return $r[0];
    }
    return '';
}

$content = "<title>Hello World</title>";

echo GetBetween($content,"<title>","</title>");

However, it only finds 1 value. If the page includes same multiple tags, how can I get them all ?

Answer 1

You can achive this using preg_replace_callback()

example:

function myFunction($match)
{  
    //$match[1] means without the <title> tags.
    //you can test with using var_dump($match)

    return $match[1];
}

$content = "<title>Hello World</title>";
$result = preg_replace_callback('#\<title\>(.+?)\<\/title\>#s','myFunction', $content);

echo $result;

Answer 2

In your example it would be the following:

    $html = "<title>Hello World</title><title>Hello StackOverflow</title><title></title>";
    $start = '<title>'; // I would use $tagName variable, but whatever
    $end = '</title>';
    $splitByStartParts = explode($start, $html);
    $result = [];
    foreach ($splitByStartParts as $i => $part) {
        if ($i > 0) {
            $r = explode($end, $part);
            $result[] = $r[0];
        }
    }
    return $result;

But it is much better to use regular expressions with look-arounds for this:

$html = "<title>Hello World</title><title>Hello StackOverflow</title>";
$tagName = 'title';
$regEx = "/(?<=<$tagName>).+(?=<\/$tagName>)/U";
// Note "U" RegEx flag for "Ungreedy"
preg_match_all($regEx, $html, $matches);
return $matches[0];

Which returns:

array(2) {
  [0] =>
  string(11) "Hello World"
  [1] =>
  string(19) "Hello StackOverflow"
}

Using regular expressions provides you with more neat and readable code, and contains all logic which is needed to identify a match in one string.

For example, if you need to gather only non-empty values (as done in the example above), you use .+ in your expression, whereas if you need all values, including empty ones, you just change that to .*. But, if expressed in PHP code, that would add yet another expression, and pieces of code handling such edge cases can (and usually do) lead to unobvious errors if accumulated.