(PHP 5 >= 5.1.0, PHP 7, PHP 8)
XMLReader::lookupNamespace — Lookup namespace for a prefix
$prefix): ?stringLookup in scope namespace for a given prefix.
prefixString containing the prefix.
   The value of the namespace, or null if no namespace exists.
  
| Version | Description | 
|---|---|
| 8.0.0 | This function can no longer return false. |