$re = '/\"(https?.+?\.(jpe?g|gif|png))\"/mi';
$str = '<a href="https://website.com/wp-content/uploads/2018/09/image-image.image.jpg"><img class="alignnone size-medium wp-image-11275" src="https://website.com/wp-content/uploads/2018/09/image-image.image-300x200.jpg" alt="" width="300" height="200" /></a> <a href="https://kids-at-home.ch/wp-content/uploads/2018/09/image2-image2-image2.jpg"><img class="alignnone size-medium wp-image-11271" src="https://kids-at-home.ch/wp-content/uploads/2018/09/image2-image2-image2.jpg-300x200.jpg" alt="" width="300" height="200" />
';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
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