PHP Strict Errors

Question

I get these PHP errors in error_log all the time and can't figure out how to solve it:

Errors:

PHP Strict Standards:  Non-static method wf_gmap::check_wp_footer() should not be called statically in /home/USERNAME/public_html/WEBSITE/wp-content/plugins/5sec-google-maps/5sec-gmaps.php on line 25

PHP Notice:  Use of undefined constant is_admin - assumed 'is_admin' in /home/USERNAME/public_html/WEBSITE/wp-content/plugins/5sec-google-maps/5sec-gmaps.php on line 21

PHP Strict Standards:  call_user_func_array() expects parameter 1 to be a valid callback, non-static method wf_gmap::init() should not be called statically in /home/USERNAME/public_html/WEBSITE/wp-includes/plugin.php on line 429

and 5sec-gmaps.php file's lines from 17 to 44 is this:

class wf_gmap {
  static $js_functions = '';

public function init() {
if(is_admin) {
  add_filter('plugin_row_meta', array(__CLASS__, 'plugin_meta_links'), 10, 2);
}
// check wp_footer()
self::check_wp_footer();

// add shortcode
global $shortcode_tags;
if (isset($shortcode_tags[GMAP_SHORTCODE])) {
  add_action('admin_footer', array(__CLASS__, 'warning'));
} else {
  add_shortcode(GMAP_SHORTCODE, array(__CLASS__, 'shortcode'));
}

// add JS include files
add_action('wp_footer', array(__CLASS__, 'footer'), 2);

// add shortcode support in sidebar text widget
if (has_filter('widget_text', 'do_shortcode') === false) {
  add_filter('widget_text', 'do_shortcode');
}

return;

and plugin.php's line from 418 to 434:

    // Sort
if ( !isset( $merged_filters[ $tag ] ) ) {
    ksort($wp_filter[$tag]);
    $merged_filters[ $tag ] = true;
}

reset( $wp_filter[ $tag ] );

do {
    foreach ( (array) current($wp_filter[$tag]) as $the_ )
        if ( !is_null($the_['function']) )
            call_user_func_array($the_['function'], array_slice($args, 0, (int) $the_['accepted_args']));

} while ( next($wp_filter[$tag]) !== false );

array_pop($wp_current_filter);

Any help would be appreciated.

Answer 1

You are invoking member methods with static context.

self::check_wp_footer(); should be $this->check_wp_footer();

Likewise, whatever $the_['function'] must be referring to a static method as well.

Answer 2

PHP Strict Standards: Non-static method wf_gmap::check_wp_footer() should

means function check_wp_footer is not static method so you can't call like this