如何在模式中的preg_replace中使用变量？

Question

I have XML in string like this:

<a:b>
  <a:c></a:c>
  <a:c></a:c>
</a:b>

and I would like to remove all data inside namespace 'a'.

Of course this can be done this way:

/<\ba\b:.*?>.*?<\/\ba\b:.*?>/

But in this case result is:

  <a:c></a:c>
</a:b>

because the first closing tag for namespace 'a' is actually a child element. So doing it recursively would live '' inside my string.

So the idea I had was to use variable in pattern the same way as you can use it in replacement:

/<(\ba\b:.*?)>.*?<\/$1>/

This is a non working solution used just to represent the idea of realisation.

All your help, ideas, ... are very welcome. Thank you for your answer in advance.

Answer 1

To directly answer the question, here is a reduced working example :

(?P<nodeOpen><a:(?P<nodeName>.*)>)(?P<data>.*)(?P<nodeClose><\/a:(?P=nodeName)>)

Used in php code :

preg_match('#(?P<nodeOpen><a:(?P<nodeName>.*)>)(?P<data>.*)(?P<nodeClose><\/a:(?P=nodeName)>)#s', $xml, $matches);

/* Produce :

array(9) {
  [0]=>
  string(43) "<a:b>
  <a:c></a:c>
  <a:c></a:c>
</a:b>"
  ["nodeOpen"]=>
  string(5) "<a:b>"
  [1]=>
  string(5) "<a:b>"
  ["nodeName"]=>
  string(1) "b"
  [2]=>
  string(1) "b"
  ["data"]=>
  string(32) "
  <a:c></a:c>
  <a:c></a:c>
"
  [3]=>
  string(32) "
  <a:c></a:c>
  <a:c></a:c>
"
  ["nodeClose"]=>
  string(6) "</a:b>"
  [4]=>
  string(6) "</a:b>"
}

*/

And then concat :

$emptyNode = $matches['nodeOpen'] . $matches['nodeClose'];

Can be consulted live here : https://regex101.com/r/xX1uZ9/2

I also recommend you the awesome talk of the amazing spiderman Jordi Boggiano available on youtube ( https://www.youtube.com/watch?v=ayo8zDnd-m8 )