(PHP 5, PHP 7, PHP 8)
php_user_filter::onCreate — Called when creating the filter
This method is called during instantiation of the filter class object. If your filter allocates or initializes any other resources (such as a buffer), this is the place to do it.
   When your filter is first instantiated, and
   yourfilter->onCreate() is called, a number of properties
   will be available as shown in the table below.
  
| Property | Contents | 
|---|---|
| FilterClass->filtername | A string containing the name the filter was instantiated with. Filters may be registered under multiple names or under wildcards. Use this property to determine which name was used. | 
| FilterClass->params | The contents of the paramsparameter passed
        to stream_filter_append()
        or stream_filter_prepend(). | 
| FilterClass->stream | The stream resource being filtered. Maybe available only during
        filter() calls when the closingparameter is set tofalse. | 
此函数没有参数。
