Fatal error: Curly braces?

[RandomTurtle]

Fatal error: Array and string offset access syntax with curly braces is no longer supported in D:\D\htdocs\index.php on line 180

what's a curly braces?

I replaced the $_iflags{$i} with $_iflags[$i] but now the page loads as a blank white page.

[Quix0r]

A curly brace {} is for function/method or whole class bodies. It also is for enclosing code in if() or else() blocks and other control/loop blocks, like while(), for(), foreach() et cetera. Replacing them with brackets ([]) will tell PHP to interpret $_iflags as an array. A white empty page indicates a fatal error which means you should reverse your changes and check log files.

[Quix0r]

$_iflags is of type string here and access on its parts also known as "sub-strings" through curly braces is no longer supported by newer PHP versions. Someone needs to rewrite this code to use substr() instead.

Plus all these type castings (int)(bool) looks odd to me.

Here is a wonderful article about it:
https://stackoverflow.com/questions/59158548/array-and-string-offset-access-syntax-with-curly-braces-is-deprecated

And yes, you can use $string[$pos] syntax instead. I get an exit code 255 here with [] instead of {}.