Source

File: wp-includes/functions.php

function wp_direct_php_update_button() {
	$direct_update_url = wp_get_direct_php_update_url();

	if ( empty( $direct_update_url ) ) {
		return;
	}

	echo '<p class="button-container">';
	printf(
		'<a class="button button-primary" href="%1$s" target="_blank" rel="noopener noreferrer">%2$s <span class="screen-reader-text">%3$s</span><span aria-hidden="true" class="dashicons dashicons-external"></span></a>',
		esc_url( $direct_update_url ),
		__( 'Update PHP' ),
		/* translators: Accessibility text. */
		__( '(opens in a new tab)' )
	);
	echo '</p>';
}