wordpress change excerpt length

function wpex_get_excerpt( $args = array() ) {

	// Defaults
	$defaults = array(
		'post'            => '',
		'length'          => 40,
		'readmore'        => false,
		'readmore_text'   => esc_html__( 'read more', 'text-domain' ),
		'readmore_after'  => '',
		'custom_excerpts' => true,
		'disable_more'    => false,
	);

	// Apply filters
	$defaults = apply_filters( 'wpex_get_excerpt_defaults', $defaults );

	// Parse args
	$args = wp_parse_args( $args, $defaults );

	// Apply filters to args
	$args = apply_filters( 'wpex_get_excerpt_args', $defaults );

	// Extract
	extract( $args );

	// Get global post data
	if ( ! $post ) {
		global $post;
	}

	// Get post ID
	$post_id = $post->ID;

	// Check for custom excerpt
	if ( $custom_excerpts && has_excerpt( $post_id ) ) {
		$output = $post->post_excerpt;
	}

	// No custom excerpt...so lets generate one
	else {

		// Readmore link
		$readmore_link = '<a href="' . get_permalink( $post_id ) . '" class="readmore">' . $readmore_text . $readmore_after . '</a>';

		// Check for more tag and return content if it exists
		if ( ! $disable_more && strpos( $post->post_content, '<!--more-->' ) ) {
			$output = apply_filters( 'the_content', get_the_content( $readmore_text . $readmore_after ) );
		}

		// No more tag defined so generate excerpt using wp_trim_words
		else {

			// Generate excerpt
			$output = wp_trim_words( strip_shortcodes( $post->post_content ), $length );

			// Add readmore to excerpt if enabled
			if ( $readmore ) {

				$output .= apply_filters( 'wpex_readmore_link', $readmore_link );

			}

		}

	}

	// Apply filters and echo
	return apply_filters( 'wpex_get_excerpt', $output );

}