CS Store is like the default buy menu, but with a difference.
your currency is Credits which is earned by killing enemies,
the prices of guns/items should always be high as once you purchase
them they are stored into your inventory permanetly, and can be equiped
every round ( but only once ), items/guns can also be refunded or gifted.

To use the API function you need to include the file thats attached cs-store.inc
into the plugin you want it to work in. then use these natives
get_user_credits( id ); will return the players current credits
give_user_credits( id, 100 ); will return giving the player 100 more credits
save_user_credits( id ); will return saving the users current credit count

Example Of Using API

Code:

#include <amxmodx>
#include <cs-store> // remember to include this file to use API correctly

#define PLUGIN "Example API Use"
#define VERSION "1.0"
#define AUTHOR "Blizzard"

public plugin_init() {
    register_plugin(PLUGIN, VERSION, AUTHOR);
    
    register_clcmd( "say /credits", "Clcmd_ShowCredits", 0 );
    register_clcmd( "say /give", "Clcmd_GiveCredits", 0 );
    register_clcmd( "say /save", "Clcmd_SaveCredits, 0 );
}

public Clcmd_ShowCredits( id ) {
    client_print( id, print_center, "Credits %i", get_user_credits( id ) );
}

public Clcmd_GiveCredits( id ) {
    give_user_credits( id, 100 );
}

public Clcmd_SaveCredits( id ) {
    save_user_credits( id );
} 

say /store - opens up the CS Store Main Menu to select a catagory to buy from.
say /shop - opens up the CS Store Main Menu to select a catagory to buy from.
say /inv - opens up the CS Store Inventory Menu to select either Equip, Refund, Gift ( to player ).
say /inventory - opens up the CS Store Inventory Menu to select either Equip, Refund, Gift ( to player ).
say /credits - enables or disables showing the HUD Message of how many credits you have.
say /help - opens up a MOTD window showing the plugin commands and what they do.

Spoiler

//////////////////////////////////////////////////////
//
// CS Store Config Settings Start
//
//////////////////////////////////////////////////////

// Save Credits After Map Change
cs_store_credits_save "0"

// Amount Of Credits Per Kill/HS Kill
cs_store_kill_bonus "1"
cs_store_hs_bonus "2"
cs_store_lowhp_bonus "3"

// Time Between Adverts
cs_store_advert_time "60.0" // Must Be Decimal Number

// CS Store Item Credit Costs
// Pistol Credit Cost
cs_store_usp "10"
cs_store_glock "10"
cs_store_deagle "10"
cs_store_p228 "10"
cs_store_elite "10"
cs_store_fiveseven "10"

// Shotgun Credit Cost
cs_store_pumpshotgun "15"
cs_store_autoshotgun "20"

// SMG Credit Cost
cs_store_mp5 "25"
cs_store_tmp "25"
cs_store_p90 "25"
cs_store_mac10 "25"
cs_store_ump "25"

// Rifle Credit Cost
cs_store_famas "30"
cs_store_sg552 "30"
cs_store_ak47 "30"
cs_store_m4al "30"
cs_store_aug "30"
cs_store_scout "30"
cs_store_awp "35"
cs_store_g3sg1 "35"
cs_store_sg550 "35"
cs_store_galil "30"

// Machine Gun Credit Cost
cs_store_m249 "40"

// Equipment Credit Cost
cs_store_kevlar "10"
cs_store_assaultsuit "15"
cs_store_flashbang "15"
cs_store_hegrenade "20"
cs_store_smokegrenade "15"
cs_store_defuse "15"
cs_store_goggles "15"
cs_store_shield "25"
////////////////////////////////////////
//
// CS Store Config Settings End
//
////////////////////////////////////////

ConnorMcleod

- enum optimize and nVault save/load optimize.
- suggesting putting stocks in sma instead of inc file.

hornet - help with API

You must compile this plugin locally with provided include file. - now you can compile from Get Plugin Link

You must place csstore.cfg file in your addons\amxmodx\configs\ directory.

I've Added The CS Store Logo image incase my hosting of the image is ever disrupted.