Untitled

<?
    $string = '
    Some photos<br>
    <span class="naslov_slike">photo_by_ile_IMG_1676-01</span><br />
    <span class="naslov_slike">photo_by_ile_IMG_1699-01</span><br />
    <span class="naslov_slike">photo_by_ile_IMG_1697-01</span><br />
    <span class="naslov_slike">photo_by_ile_IMG_1695-01</span><br />
    ';

    $dom = new DOMDocument();
    $dom->loadHTML($string);
    $dom->preserveWhiteSpace = false;
    $elements = $dom->getElementsByTagName('span');
    $spans = array();
    foreach($elements as $span) {
        $spans[] = $span;
    }
    foreach($spans as $span) {
        $span->parentNode->removeChild($span);
    }
    echo $dom->saveHTML();


?>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/REC-html40/loose.dtd">
<html><body><p>Some photos<br><br><br><br><br></p></body></html>

<?php

function innerHTML($node){
  $doc = new DOMDocument();
  foreach ($node->childNodes as $child)
    $doc->appendChild($doc->importNode($child, true));

  return $doc->saveHTML();
}

 $string = '
    Some photos<br>
    <span class="naslov_slike">photo_by_ile_IMG_1676-01</span><br />
    <span class="naslov_slike">photo_by_ile_IMG_1699-01</span><br />
    <span class="naslov_slike">photo_by_ile_IMG_1697-01</span><br />
    <span class="naslov_slike">photo_by_ile_IMG_1695-01</span><br />
    ';

    $dom = new DOMDocument();
    $dom->preserveWhiteSpace = false;
    $dom->loadHTML($string);
    $elements = $dom->getElementsByTagName('span');
    $spans = array();
    foreach($elements as $span) {
        $spans[] = $span;
    }
    foreach($spans as $span) {
        $span->parentNode->removeChild($span);
    }

    echo innerHTML( $dom->documentElement->firstChild );

<p>Some photos<br><br><br><br><br></p>

# loadHTML causes a !DOCTYPE tag to be added, so remove it:
$dom->removeChild($dom->firstChild);

# it also wraps the code in <html><body></body></html>, so remove that:
$dom->replaceChild($dom->firstChild->firstChild->firstChild, $dom->firstChild);

echo preg_replace("/<!DOCTYPE [^>]+>/", "", $dom->saveHTML());

$html_fragment = preg_replace('/^<!DOCTYPE.+?>/', '', str_replace( array('<html>', '</html>', '<body>', '</body>'), array('', '', '', ''), $dom->saveHTML()));