使用 PHP 替换平面文件数据库中的一行

Question

There are quite a few different threads about this similar topic, yet I have not been able to fully comprehend a solution to my problem.

What I'd like to do is quite simple, I have a flat-file db, with data stored like this -

$username:$worldLocation:$resources

The issue is I would like to have a submit data html page that would update this line based upon a search of the term using php

search db for - $worldLocation

if $worldLocation found

replace entire line with $username:$worldLocation:$updatedResources

I know there should be a fairly easy way to get this done but I am unable to figure it out at the moment, I will keep trying as this post is up but if you know a way that I could use I would greatly appreciate the help.

Thank you

Answer 1

I always loved c, and functions that came into php from c.

Check out fscanf and fprintf .

These will make your life easier while reading writing in a format. Like say:

$filehandle = fopen("file.txt", "c");
while($values = fscanf($filehandle, "%s\t%s\t%s\n")){
    list($a, $b, $c) = $values;
    // do something with a,b,c
}

Also, there is no performance workaround for avoiding reading the entire file into memory -> changing one line -> writing the entire file . You have to do it.

This is as efficient as you can get. Because you most probably using native c code since I read some where that php just wraps c's functions in these cases.

Answer 2

1. You like the hard way so be it....
2. Make each line the same length. Add space, tab, capital X etc to fill in the blanks
3. When you want to replace the line, find it and as each line is of a fixed length you can replace it.
4. For speed and less hassle use a database (even SQLLite)

Answer 3

If you're committed to the flat file, the simplest thing is iterating through each line, writing a new file & changing the one that matches.

Yeah, it sucks.

I'd strongly recommend switching over to a 'proper' database. If you're concerned about resources or the complexity of running a server, you can look into SQLite or Berkeley DB. Both of these use a database that is 'just a file', removing the issue of installing and maintaining a DB server, but still you the ability to quickly & easily search, replace and delete individual records. If you still need the flat file for some other reason, you can easily write some import/export routines.

Another interesting possibility, if you want to be creative, would be to look at your filesystem as a database. Give each user a directory. In each directory, have a file for locations. In each file, update the resources. This means that, to insert a row, you just write to a new file. To update a file, you just rewrite a single file. Deleting a user is just nuking a directory. Sure, there's a bit more overhead in slurping the whole thing into memory.

Other ways of solving the problem might be to make your flat-file write-only, since appending to the end of a file is a trivial operation. You then create a second file that lists "dead" line numbers that should be ignored when reading the flat file. Similarly, you could easily "X" out the existing lines (which, again, is far easier than trying to update lines in a file that might not be the same length) and append your new data to the end.

Those second two ideas aren't really meant to be practical solutions as much as they are to show you that there's always more than one way to solve a problem.

Answer 4

ok.... after a few hours work..this example woorked fine for me... I intended to code an editing tool...and use it for password update..and it did the trick! Not only does this page send and email to user (sorry...address harcoded to avoid posting aditional code) with new password...but it also edits entry for thew user and re-writes all file info in new file... when done, it obviously swaps filenames, storing old file as usuarios_old.txt.

grab the code here (sorry stackoverflow got VERY picky about code posting)

https://www.iot-argentina.xyz/edit_flat_databse.txt

Answer 5

那是您所在的位置吗：

update `field` from `table` set `field to replace` = '$username:$worldlocation:$updatesResources' where `field` = '$worldLocation';