php - Blocks - curly braces/no curly braces?

When I started developing, I followed tutorials that always used {} (curly braces) to enclose blocks. However, when I began looking at other peoples code (classes on GitHub for example, or just more code in general than what a basic tutorial would show), however I've also seen block statements without being enclosed in {}, for example;

if($var < 15)
     $string = 'Hello, Jimmy!';
elseif($var >= 15)

     $string = 'Hello, Anne!';

Is the same as

if($var < 15) { 
    $string = 'Hello, Jimmy!';
} elseif($var >= 15) {
    $string = 'Hello, Anne!';
}

I've never used blocks not enclosed in {}, however I used them today and I'm starting to see the efficiency of doing so (it looks a lot cleaner too, as I'll often find my functions riddled with {} from loops, conditionals etc.

What I'm asking is;

a) are there any limitations on blocks without curly braces (; I noticed my IDE dropped back from an indent after I enter a single line and returned after an if() conditional?

b) are there any best practices to be had, when not using {}?

Any answers, specifically those inc. background/docs on the convention of curly brace usage for blocks vs. not using them would be greatly appreciated, as I'd really like to understand the usage of curly braces :)!

Answer

You can omit the {} for one single line:

if(something)
  do something else

however you cannot omit it and have it keep going like so:

if(something)
   do one thing
   do another
   do some more

The example above would only have 1 conditional element (the 'do one thing'). The rest would just run unconditionally.

And yes I've seen the sloppy method before without the {}, I myself prefer using {} to separate the logic, and its easier to read.

So stick to using {} in your code.