Module development and code questions

I have installed search_api, search_api_solr and search_api_attachments. Also have Solr v.8.4.0 installed.

I installed php SolrClient for Centos 7 following this guidance: https://stackoverflow.com/questions/22959330/fatal-error-class-solrclient-not-found , but I still get "Class 'SolrClient' not found" every time I run

I am trying to turn off entity caching for a custom entity in 8.7.3. This is an existing entity if that matters. Described via:

 * @ContentEntityType(
 *   id = "shift",
 *   label = @Translation("Shift"),
 *   base_table = "scheduler_entity_shifts",
 *   entity_keys = {
 *     "id" = "id",
 *     "uuid" = "uuid",
 *   },
 *   static_cache = FALSE,
 *   persistent_cache = FALSE,
 *   translatable = FALSE,
 * )

I added the last 3 lines. I have added a hook:

Trying to find a simple way to add via hook possibly within mymodulename_search_api_solr_search_results_alter to hide a specific site page from internal search results. I'm finding suggestions for modules but is there a simpler way to hide a page?

How to save a text file in database by taking input through form?

Scenario

Site building:

• Taxonomy: Vocabulary 'Countries' (around 300 terms, one for each country).
• Content type Office: with a taxonomy reference field to Countries, so you can tag an office with a country.
• View: showing Offices with an exposed filter on Countries taxonomy.

Front:

• In the view's page, you filter by 100 countries to get the Offices in that countries.

Result:

Hi,

I have to merge contents from few nodes and write them in a file. I have to then download the file as pdf. Everything needs to be done programmatically. 

I have searched for examples to help me with it, but have not found any helpful ones.

Could you please let me know how to write the contents in a file and then let a user to download the file as pdf?

Thanks,