If you need to find a file anywhere on a server, what directory it is in or not, the Linux Find command is your go to command! Here are some basic usage cases:
Find a file in the current directory:
find . -name "this-file.php"
Find a file anywhere on the server above the root directory:
find / -name "filename.php"
Notice in the first example we used a period and in the second we used a forward slash. The period means to search the current directory and the forward slash means to search from the root directory and will basically find a file anywhere on the file in the root directory or any of its sub-directories.
Perform a case-insensitive search:
The above commands all use the -name parameter which performs a case-sensitive search. To perform a case-insensitive search, replace -name with -iname in the above examples, like so:
find / -iname "filename.php"
Perform a wildcard search:
The wildcard character is *. If you want to find all .php files, for example, use the following command:
find / -iname "*.php"