$re = '/(<img\s[\w\d\W]+?>){1,}/';
$str = 'text text text text text <img scr="kotik.jpg" alt="котяра"/> text text text
text text text text text <img scr="pesik.jpg" alt="пёс"/><img scr="popugaichik.jpg" alt="птица"/><img scr="zmeika.jpg" "змея"/> text text text
';
$subst = "<div class=\"some_class\">$0</div>";
$result = preg_replace($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