How to echo a different title to the page if it’s opened on an android mobile phone

I’m not sure where this php_browser_info() function comes from.

You can try the following instead:

/**
 * Modify the front/home page title for Android devices
 */
add_filter( 'wp_title', function( $title )
{
    return
        ( is_front_page() || is_home() )
        && isset( $_SERVER['HTTP_USER_AGENT'] ) 
        && false !== stripos( $_SERVER['HTTP_USER_AGENT'], 'android' )
        ? 'Test Android'
        : $title;
}, PHP_INT_MAX );

to modiy the title of the front page. Here we use a modification of the Android check from the wp_is_mobile() function, so please note that this detection might not be that accurate!