The Ds\Deque::first() function is an inbuilt function in PHP which returns the first value in the Deque if Deque is not empty.
Syntax:
public Ds\Deque::first( void ) : mixed
Parameters: This function does not accept any parameter.
Return Value: This function returns the first element from the Deque, if the deque is not empty.
Below programs illustrate the Ds\Deque::first() function in PHP:
Program 1:
<?php   // Declare a deque $deck = new \Ds\Deque([10, 20, 3, 40, 50, 6]);   echo("Elements in the Deque\n");   // Display the Deque elements print_r($deck);   echo("\nFirst element in the deque: ");   // Use first() function to find // first element in the deque var_dump($deck->first());   ?> |
Output:
Elements in the Deque
Ds\Deque Object
(
[0] => 10
[1] => 20
[2] => 3
[3] => 40
[4] => 50
[5] => 6
)
First element in the deque: int(10)
Program 2:
<?php   // Declare a deque $deck = new \Ds\Deque(["Geeks", "for", "GFG"]);   echo("Elements in the Deque\n");   // Display the Deque elements print_r($deck);   echo("\nFirst element in the deque: ");   // Use first() function to find // first element in the deque var_dump($deck->first());   ?> |
Output:
Elements in the Deque
Ds\Deque Object
(
[0] => Geeks
[1] => for
[2] => GFG
)
First element in the deque: string(5) "Geeks"
Reference: http://php.net/manual/en/ds-deque.first.php
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