CachingIterator::offsetExists
  (PHP 5 >= 5.2.0, PHP 7, PHP 8)
CachingIterator::offsetExists — The offsetExists purpose
  
 
  说明
  
   public CachingIterator::offsetExists(
string $key): 
bool 
  
  
  
  
 
  参数
  
   
    
     key 
     - 
      
       The index being checked.
      
      
    
   
  
  
 
  返回值
  
   Returns true if an entry referenced by the offset exists, false otherwise.