如何在wordpress插件中修复“不能在写入上下文中使用函数返回值”

Question

I've downloaded an older plugin for WordPress but whenever I try to activate it throws this error:

Fatal error: Can't use function return value in write context in [filelocation] line 41

function poa_ps_enqueue_scripts() {


    if ( is_category() ) :
        $cat = get_category(get_query_var('cat'));
        $slides_loop = new WP_Query( array( 'post_type' => POA_POST_TYPE_NAME, 'category__in' => $cat->term_id, 'posts_per_page' => -1, 'order' => 'asc' ) );
        if ( !empty($slides_loop) ) :

            wp_enqueue_style( 'reveal_preloader_css', POA_PLUGIN_URL . '/css/preloader.css', array(), '2017' );
            wp_enqueue_style( 'reveal_css', POA_PLUGIN_URL . '/js/libs/reveal/css/reveal.css', array(), '2017' );
            // reveal.js scripts
            wp_register_script( 'reveal_js', POA_PLUGIN_URL . '/js/libs/reveal/js/reveal.js', array('jquery'), '3.7.3', '1.0', true );
            wp_enqueue_script( 'reveal_js' );

            wp_enqueue_style( 'reveal_custom_css', POA_PLUGIN_URL . '/css/poa_style.css', array(), '20160816' );

            wp_register_script( 'reveal_speaker_notes_js', POA_PLUGIN_URL . '/js/libs/reveal/plugin/notes/notes.js', array(), null, true );
            wp_enqueue_script( 'reveal_speaker_notes_js' );

            // reveal.js current config and work
            wp_register_script( 'reveal_front_js', POA_PLUGIN_URL . '/js/front-js.js', array(), '3.7.3', true );

            // get plugin options from admin page Settings->Presentation Slides
Error->     $autoslide = isset(get_option('poa_option_name')['poa_enable_autoslide']) ? get_option('poa_option_name')['poa_enable_autoslide'] : 0;
            $loop = isset(get_option('poa_option_name')['poa_enable_continuous_loop']) ? get_option('poa_option_name')['poa_enable_continuous_loop'] : 0;
            $transition = isset(get_option('poa_option_name')['poa_slides_transition']) ? get_option('poa_option_name')['poa_slides_transition'] : 0;

            // Localize the script with new data
            $php_vars = array(
                'enable_autoslide' => intval( $autoslide ),
            //  'autoslide_time' => esc_html( of_get_option('reveal_autoslide_time') ),
                'loop_presentation' => intval( $loop ),
                'transition' => esc_html($transition)
            );
            wp_localize_script( 'reveal_front_js', 'php_vars', $php_vars );

            wp_enqueue_script( 'reveal_front_js' );

            if (!empty(get_option('poa_option_name')['poa_position_navigation'])) {
                $position = esc_html(get_option('poa_option_name')['poa_position_navigation']);
                if ($position == 'left' || $position == 'right') {
                    wp_enqueue_style( 'position_css', POA_PLUGIN_URL . '/css/poa-position-nav.css', array(), '2017' );
                }
            }
            endif;
    endif; //is_category()
}

Anyone know how i can fix this? The wordpress site is also telling me i'm running a older version of PHP could this be connected too the error? And if so can it be fixed without updating PHP?