$re = '/<span id=pink>.*?<\/span>(.*?)(?=<span|$)/s';
$str = '<span id=pink>some short text</span>
more text that can be a few lines
<span id=pink>again a short text</span>
More text that\'s abiding the same logic
<span id=pink>Repeat</span>...(more of these)';
$subst = "";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php