PHP | SplDoublyLinkedList valid() Function

The SplDoublyLinkedList::valid() function is an inbuilt function in PHP which is used to check whether the doubly linked list contains more nodes or not.

Syntax:

bool SplDoublyLinkedList::valid( void )

Parameters: This function does not accept any parameters.

Return Value: This function returns TRUE if the doubly linked list contains any more nodes and FALSE otherwise.

Below programs illustrate the SplDoublyLinkedList::valid() function in PHP:
Program 1:



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<?php
   
// Declare an empty SplDoublyLinkedList 
$list = new SplDoublyLinkedList();
   
// Use SplDoublyLinkedList::push() function to  
// add elements to the SplDoublyLinkedList 
$list->push(1); 
$list->push(2); 
$list->push(3); 
$list->push(8); 
$list->push(5); 
  
$list->rewind();
  
for($i = 0; $i < 5; $i++) {
    if($list->valid())
        echo $list->current() . " ";
      
    $list->next();
}
  
?>

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Output:

1 2 3 8 5

Program 2:

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<?php
   
// Declare an empty SplDoublyLinkedList 
$list = new SplDoublyLinkedList();
   
// Use SplDoublyLinkedList::add() function
// to add the element into the list
$list->add(0, "Welcome"); 
$list->add(1, "to"); 
$list->add(2, "GeeksforGeeks"); 
$list->add(3, "A"); 
$list->add(4, 'Computer'); 
$list->add(5, "Science"); 
$list->add(6, 'Portal'); 
   
$list->rewind();
  
for($i = 0; $i < 7; $i++) {
    if($list->valid())
        echo $list->current() . " ";
      
    $list->next();
}
  
?>

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Output:

Welcome to GeeksforGeeks A Computer Science Portal

Reference: https://www.php.net/manual/en/spldoublylinkedlist.valid.php




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