How to properly escape a variable that is used in a file path?

Question

css

I am writing a function that will use the file name, but I don’t know how to escape it correctly, because the variable is seen as text

function massive_csv($file_name){
$arr = file('./$file_name.csv'){

Answer 1

Most conveniently, an after pseudo-element with a gradient. The shadow is not very convenient, because. the sides will stick out a little.

Answer 2

1. replace quotes with double quotes
   
2. wrap the variable in curly braces
   

well, as suggested below
, concatenation -- glue a string and a variable

Answer 3

function massive_csv($file_name){
$arr = file('./' . $file_name . '.csv'){

m?