How to write a regular expression with replacement?

Question

PHP

It is necessary to leave only emails like [mailto:[email protected] [email protected]], how to do it?

$str = "
 [email protected]
  [mailto:[email protected] [email protected]]
";

$target_str = " (?!\[mailto\:)([a-z0-9._%+-][email protected](?:[A-Z0-9-]+\.)+[A-Z]{2,}(?!\]))(?!\])";
$replacement_str = " [mailto:$1 $1]";
$num_matches = 0;
$str2 = preg_replace( '/' . $target_str . '/ui', $replacement_str, $str , -1, $num_matches );
echo $str;
echo $str2;

The logic is this. If there is an email in the text, then replace it with a pattern
; if there is a pattern, then leave it as it is.
The problem is that the regular expression grabs the second email and replaces it according to the pattern.
sandbox

Answer 1

$pattern = '/[\w.%+-][email protected](?:[a-z\d-]+\.)+[a-z]{2,}|\[mailto:[^\]]+(*SKIP)(*F)/i';

$str = preg_replace($pattern, '[mailto:$0]', $str);

sandbox.onlinephpfunctions.com/code/cd3b7b636cde9b...