The **`first()`** method of the `DS\Vector` class in PHP returns the first value present in a vector.

The process is illustrated below:

The prototype of the `first()` method is shown below:

```php
mixed public Ds\Vector::first( void )
``` 

<h2>Parameters</h2>

The `first()` method does not accept any parameters.

<h2>Return value</h2>

The `first()` method returns the first value present in a vector. This value can have any data type.

If the vector does not contain any values, the `first()` method throws the [UnderflowException](https://www.php.net/manual/en/class.underflowexception.php).

<h2>Example</h2>

The code below shows how the `first()` method works in PHP:

<?php

// initialize vectors
$firstVector = new \Ds\Vector([1, 5, 8, 10, 15]);
$secondVector = new \Ds\Vector(["abc", 2, 10, true, false]);

// find and print first value of each vector
print_r($firstVector);
print("The first value of the above vector is: ");
print($firstVector->first());

print("\n\n");

print_r($secondVector);
print("The first value of the above vector is: " );
print($secondVector->first());

?>

The above code produces the following output:

```php
Ds\Vector Object
(
[0] => 1
[1] => 5
[2] => 8
[3] => 10
[4] => 15
)
The first value of the above vector is: 1

Ds\Vector Object
(
[0] => abc
[1] => 2
[2] => 10
[3] => 1
[4] =>
)
The first value of the above vector is: abc
```

> **Note**: To run this program, you need to install [Data Structures](https://www.php.net/manual/en/book.ds.php) for PHP on your local machine.

<h2>Explanation</h2>

First, two vectors are initialized: `firstVector` and `secondVector`.

The `first()` method in line $10$ finds and returns the first value of `firstVector`, i.e., the integer $1$.

Similarly, the `first()` method in line $16$ finds and returns the first value of `secondVector`, i.e., the string `abc`.



What is the DS\Vector first() method in PHP?

The first() method of the DS\Vector class in PHP returns the first value present in a vector. The process is illustrated below: 