Replacement for nested IF's? - php

Question

Sometimes mostly for processing user input i find myself using a lot of IF statements nested in each other, sometimes it is much more than below, to the point it goes from if on left side of screen to the if number 10 on right side of screen.
This is very difficult to read and troubleshoot, is there other way to do nested if?
I know about switch() however in this case i have to do query in third if rather than first.
if (true) {
if (true) {
if (true) {
...
echo "You are logged in";
} else {
echo "login failed"
}
} else {
echo "incorrect email";
}
}

Answer 1

I assume that your true conditions are real conditions, and not just the true boolean constant.
if (condition1 && condition2 && condition3) {
echo "You are logged in";
} else {
echo "login failed";
}
If you need a condition handled separately:
if (emailAddressIsCorrect) {
if (condition2 && condition3) {
echo "You are logged in";
} else {
echo "login failed";
} else {
echo "incorrect email";
}
Or you can just return early, which is cleaner in my opinion. You can do this for each condition, if you like. You can have as many conditions as you want with this arrangement, without requiring condition nesting:
if (!emailAddressIsCorrect) {
echo "incorrect email";
return;
}

Answer 2

Often times I'll do the "fail out" strategy instead:
function login() {
if (!condition1) {
echo "incorrect email";
return false;
}
if(!condition2) {
echo "incorrect password";
return false;
}
if(condition3) {
echo "logged in successfully!";
return true;
}
return false;
}
This example is suspect, there are security concerns with letting an attacker know which part of the login failed, but as a code snippet, you can see the strategy.

Answer 3

Combine 2 if statements using "&&".
OR
Sometimes using object oriented programming you can avoid if statements:
if(is type a) {
dostuff1();
} else if(is type b) {
dostuff2();
}
With classes and inheritance:
class->dostuff();
You can also use "first class functions" to avoid if statements.
Say you have values $_POST['page'] == 'page1', $_POST['page'] == 'page2'
$functions = array("page1"=>$function1, "page2"=>$function2);
function dostuff1() {
return 'a';
}
function dostuff2() {
return 'b';
}
$function1 = "dostuff1";
$function2 = "dostuff2";
$functions[$_POST['page']]();
instead of
if($_POST['page'] == '1') dostuff1();
etc... although this method is somewhat scary... lol

Answer 4

compare this:
if ($true1) {
if ($true2) {
if ($true3) {
...
with this:
if ($true1 && $true2 && $true3) {
...
}
with the first appoach not only you're wasting useful space for a single IF,
you are also delaying the inevitable: the optimization at a later day.
Also, it has no matter (etc. performance) if you place your IFs as nested or
in a single line because PHP intepreter will stop checking beyond if it finds
a FALSE.