preg_replace匹配所有但第一次出现的东西？

Question

I'm looking for a way to replace all but first occurrences of a group or some character.

For example a following random string:

+Z1A124B555ND124AB+A555

1,5,2,4,A,B and + are repeating through out the string.

124, 555 are groups of characters that are also reoccurring.

Now, let's say I want to remove every but first occurrence of 555, A and B.

What regex would be appropriate? I could think of an example replacing all:

preg_replace('/555|A|B/','',$string);

Something like ^ that, but I want to keep the first occurrence... Any ideas?

Answer 1

Are your strings always delimited by plus signs? Do 555, A, and B always occur in the first "group" (delimited by +)?

If so, you can split, replace and then join:

$input = '+Z1A124B555+A124AB+A555';
$array = explode('+', $input, 3); // max 3 elements
$array[2] = str_replace(array('555', 'A', 'B'), '', $array[2]);
$output = implode('+', $array);

ps. No need to use regexes, when we can use a simple str_replace

---

Use the preg_replace_callback function:

$replaced = array('555' => 0, 'A' => 0, 'B' => 0);
$input = '+Z1A124B555+A124AB+A555';
$output = preg_replace_callback('/555|[AB]/', function($matches) {
  static $replaced = 0;
  if($replaced++ == 0) return $matches[0];
  return '';
}, $input);