Simple: How to replace "all between" with php?

Question

$string = "<tag>i dont know what is here</tag>"
$string = str_replace("???", "<tag></tag>", $string);
echo $string; // <tag></tag>

So what code am i looking for?

Answer 1

A generic function:

function replace_between($str, $needle_start, $needle_end, $replacement) {
    $pos = strpos($str, $needle_start);
    $start = $pos === false ? 0 : $pos + strlen($needle_start);

    $pos = strpos($str, $needle_end, $start);
    $end = $pos === false ? strlen($str) : $pos;

    return substr_replace($str, $replacement, $start, $end - $start);
}

DEMO

Answer 2

$search = "/[^<tag>](.*)[^<\/tag>]/";
$replace = "your new inner text";
$string = "<tag>i dont know what is here</tag>";
echo preg_replace($search,$replace,$string);

outputs:

<tag>your new inner text</tag>

Answer 3

$string = "<tag>I do not know what is here</tag>";
$new_text = 'I know now'; 
echo preg_replace('#(<tag.*?>).*?(</tag>)#', '$1'.$new_text.'$2' , $string); //<tag>I know now</tag>

Answer 4

A generic and non-regex solution:

I've modified @felix-kling's answer. Now it only replaces text if it finds the needles.

Also, I've added parameters for replacing the needles, starting position and replacing all the matches.

I've used the mb_ functions for making the function multi-byte safe. If you need a case insensitive solution then replace mb_strpos calls with mb_stripos.

function replaceBetween($string, $needleStart, $needleEnd, $replacement,
                        $replaceNeedles = false, $startPos = 0, $replaceAll = false) {
    $posStart = mb_strpos($string, $needleStart, $startPos);

    if ($posStart === false) {
        return $string;
    }

    $start = $posStart + ($replaceNeedles ? 0 : mb_strlen($needleStart));
    $posEnd = mb_strpos($string, $needleEnd, $start);

    if ($posEnd === false) {
        return $string;
    }

    $length = $posEnd - $start + ($replaceNeedles ? mb_strlen($needleEnd) : 0);

    $result = substr_replace($string, $replacement, $start, $length);

    if ($replaceAll) {
        $nextStartPos = $start + mb_strlen($replacement) + mb_strlen($needleEnd);

        if ($nextStartPos >= mb_strlen($string)) {
            return $result;
        }

        return replaceBetween($result, $needleStart, $needleEnd, $replacement, $replaceNeedles, $nextStartPos, true);
    }

    return $result;
}

$string = "{ Some} how it {is} here{";

echo replaceBetween($string, '{', '}', '(hey)', true, 0, true); // (hey) how it (hey) here{

Answer 5

If "tag" changes:

$string = "<tag>i dont know what is here</tag>";
$string = preg_replace('|^<([a-z]*).*|', '<$1></$1>', $string)
echo $string; // <tag></tag>

Answer 6

If you don't know what's inside the <tag> tag, it's possible there is another <tag> tag in there e.g.

<tag>something<tag>something else</tag></tag>

And so a generic string replace function won't do the job.

A more robust solution is to treat the string as XML and manipulate it with DOMDocument. Admittedly this only works if the string is valid as XML, but I still think it's a better solution than a string replace.

$string = "<tag>i don't know what is here</tag>";
$replacement = "replacement";

$doc = new DOMDocument();
$doc->loadXML($str1);
$node = $doc->getElementsByTagName('tag')->item(0);
$newNode = $doc->createElement("tag", $replacement); 
$node->parentNode->replaceChild($newNode, $node);
echo $str1 = $doc->saveHTML($node); //output: <tag>replacement</tag>

Answer 7

$string = "<tag>i dont know what is here</tag>"
$string = "<tag></tag>";
echo $string; // <tag></tag>

---

or just?

$string = str_replace($string, "<tag></tag>", $string);

Sorry, could not resist. Maybe you update your question with a few more details. ;)

Answer 8

If you need to replace the portion too then this function is helpful:

$var = "Nate";

$body = "Hey there {firstName} have you already completed your purchase?";

$newBody = replaceVariable($body,"{","}",$var);

echo $newBody;

function replaceVariable($body,$needleStart,$needleEnd,$replacement){
  while(strpos($body,$needleStart){
      $start = strpos($body,$needleStart);
      $end = strpos($body,$needleEnd);
      $body = substr_replace($body,$replacement,$start,$end-$start+1);
  }
  return $body;
}

I had to replace a variable put into a textarea that was submitted. So I replaced firstName with Nate (including the curly braces).