system/Pager/Pager.php
public function getPageURI(int $page = null, string $group = 'default', bool $returnObject = false)
	{
		$this->ensureGroup($group);

		/**
		 * @var \CodeIgniter\HTTP\URI $uri
		 */
		$uri = $this->groups[$group]['uri'];

		$segment = $this->segment[$group] ?? 0;

		if ($segment)
		{
			$uri->setSegment($segment, $page);
		}
		else
		{
			$uri->addQuery('page', $page);
		}

		if ($this->only)
		{
			$query = array_intersect_key($_GET, array_flip($this->only));

			if (! $segment)
			{
				$query['page'] = $page;
			}

			$uri->setQueryArray($query);
		}

		return $returnObject === true ? $uri : (string) $uri;
	}
public function getPageURI(int $page = null, string $group = 'default', bool $returnObject = false)
	{
		$this->ensureGroup($group);

		/**
		 * @var \CodeIgniter\HTTP\URI $uri
		 */
		$uri = $this->groups[$group]['uri'];

		$segment = $this->segment[$group] ?? 0;

		if ($segment)
		{
			$uri->setSegment($segment, $page);
		}
		else
		{
			$uri->addQuery('page', $page);
		}

		if ($this->only)
		{
			$query = array_intersect_key($_GET, array_flip($this->only));

			if (! $segment)
			{
				$query['page'] = $page;
			}

			$uri->setQueryArray($query);
		}

		return $returnObject === true ? $uri : (string) $uri;
	}
Returns the URI for a specific page for the specified group.

@param integer|null $page
@param string       $group
@param boolean      $returnObject

@return string|\CodeIgniter\HTTP\URI