Programming standards with safety and simplicity

Question

Maybe this question sounds broad but deep down it is not, I am not graduated in anything so I only have bad practices on my back and wanted to learn to program in a way not only "standard" and yes clear and clean.

---

Programming standards with safety and simplicity

See, when I say programming patterns, I mean how to write code in a healthy and simple way... Reading and researching I found some tips that may help, such are:

1. Write variables in a short descriptive manner and following the "camel hump model" Ex: $userBrowser = $_SERVER...
2. Comment on code, but make brief and descriptive comments for future maintenance
3. Being simplistic when it comes to making it happen, I mean, making the code the easy way without losing efficiency

I met these three, they must have others.. If you know other cite at most 3 not listed above...

and security, where you enter?

Well, I have little tic with security, fear maybe and as always I am programming on the server side (ex: PHP) and the customer (ex: JS) I am extremely concerned about that. Security is a very broad subject, so let’s summarize in "programming security", I don’t know exactly how to name what I will say but look at this situation:

this example is extremely metaphorical for explanatory purposes.

Suppose 10 different dogs are arranged in an array.

A while will item this array and play each item, dog, in a function to verify the attributes of the animal.

while....
checaAtributos(cachorro)....
....

the function checaAtributos does that:

function checaAtributos(cachorro) {
   if(cachorro.lenght == 0) // verifica se a variável cachorro está vazia...

   var corDosOlhos = checaCorDosOlhos(cachorro);
   ....

in function checaCorDosOlhos I will need to check again if the variable cachorro is empty? It is necessary?

In short: once checked certain parameters I will have to check them again if I pass from one function to another?

I think that’s it, if you have anything else to add I’ll be grateful