[Quickie]

PHP код:

public OnPlayerTakeDamage(playerid, issuerid, Float: amount, weaponid)
{
    new Float:HP,Float:gain;
    GetPlayerHealth(playerid, HP);// ex: HP==65
    if(weaponid == 25) 
    {
         gain=amount*0.25  //25 percent ex: amount(damage teken)=35 so 35*0.25==8.75
         SetPlayerHealth(playerid,HP+gain);//HP==65+8.75
    }
    return 1;
}
//overall damage dealt by shotgun==26.25 {100-73.75}regardless of original amount send by client which is 35