PHP: What do the curly braces in $variable{0} do?

Question

I was going through a codebase and came across a line I had a question about. It's something I haven't seen before and I was wondering if someone could explain it for me. Here's the code:

$variableName = $array[1];
$variableName{0} = strtolower($variableName{0});
$this->property = $variableName;

What are the curly braces being used for? I've used curly braces to define variables as variable names before, but is this the same thing? I can't seem to find any resources online that explain it, but I'm not sure if I'm searching for the right thing.

Answer 1

access the single byte with that index {0} => first char (in non-utf8 string)

you could simply test it with:

$var='hello';
echo $var{0};

Answer 2

It's setting the first character of the string to lower case. It's a string shortcut operator, functioning the same as this:

<?php
$variableName = strtolower(substr($variableName, 0, 1)) . substr($variableName, 1)