Error message

• Notice: Use of undefined constant JSON_UNESCAPED_SLASHES - assumed 'JSON_UNESCAPED_SLASHES' in structured_data_preprocess_html() (line 62 of /var/www/html/sites/all/modules/structured_data/structured_data.module).
• Warning: json_encode() expects parameter 2 to be long, string given in structured_data_preprocess_html() (line 62 of /var/www/html/sites/all/modules/structured_data/structured_data.module).