Reading and Writing to a File with a Variable Name

PPowerHouseK

Hello all,

I am very new to php, so please be nice.
I am trying to create a file for each user and have it read and write a value to that file. If that file does not exist yet, then it should create one with a value of 0 in it.

Basically each user needs their own file and file name, independent from eachother. I have attempted to do this, but my php syntax knowledge is limited so I can't seem to get it to work. Here is what I have so far:

		<?php 

	//read logon file
	If($userlogfile = NULL)
		{
		$userlogcountfile="../logs/" . $username . "logon.txt";
		$logfile=fopen( $userlogcountfile, "w");
		$logcountpower=0;
		fwrite( $logfile, $logcountpower);
		}
	$userlogcountfile="../logs/" . $username . "logon.txt";
	$logfile = fopen( $userlogcountfile, "r");
	$logfilesize = filesize ( $userlogcountfile );
	$logcount = fread( $logfile, $logfilesize );
	$logcount++;
	fclose($logfile);
	//open file for writing
	$logfile = fopen($$userlogcountfile, "w");
	fwrite( $logfile, $logcount);

	fclose($logfile);

	?>

Here is the error I am getting:

Warning: fopen(../logs/PowerHouselogon.txt) [function.fopen]: failed to open stream: No such file or directory in C:\xampp\htdocs\Pkshost0\Admins\panel.php on line 171

So what I gather is happening is its not creating the file. Perhaps my comparison to NULL isnt appropriate for file detection, i dont know. Any help would be much appreciated.

bradgrafelman

There are a few issues with your code:

When posting PHP code, please use the board's [noparse]
```
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[/noparse] bbcode tags (instead of the generic CODE tags) as they make your code much easier to read and analyze.
In your if() statement, you're using the '=' operator, which is the assignment operator. In other words, your if() statement is actually assigning a value to $userlogfile rather than comparing it's value (which is done with a comparison operator, such as '=='). See the manual page [man]operators.comparison[/man] for more info.
Speaking of the if() statement... where is $userlogfile ever defined?
How is checking if a (presently undefined) variable is equal to the NULL value giving you any sort of "file detection" ? Surely you don't expect PHP to automagically understand what you meant to do?

Instead, look at using [man]file_exists/man to check if a file already exists or not.
Seems like your logic could be optimized to make the code easier to understand as well as more efficient.

For example, once you know that the file doesn't exists, you can simply write out the '0' value and move on - there's no point in reading back the file you just wrote in order to get its value.
If you're trying to read an entire file at once, it's often more efficient and a lot easier to simply use [man]file_get_contents/man.

Likewise, [man]file_put_contents/man is often easier than doing an fopen/fwrite/fclose series.
Why do you have a double dollar sign on line #18 of your code snippet above? This should be generating error messages, so either you're ignoring them (why?!) or you don't have a very good development environment (e.g. display_errors set to On and error_reporting set to E_ALL).
Your code is technically vulnerable to a race condition, but I'd be more worried about the efficiency/consistency of the way you're storing/handling data.

In other words, why not use a database?

PPowerHouseK

When posting PHP code, please use the board's
..
bbcode tags (instead of the generic CODE tags) as they make your code much easier to read and analyze.

1) Understood I will do so in the future.

In your if() statement, you're using the '=' operator, which is the assignment operator. In other words, your if() statement is actually assigning a value to $userlogfile rather than comparing it's value (which is done with a comparison operator, such as '=='). See the manual page operators.comparison for more info.

2) I did not know that, thank you for clearing that up.

Speaking of the if() statement... where is $userlogfile ever defined?

3) I fiddled with my code some after posting, and added

$userlogcountfile="../logs/" . $username . "logon.txt";

just above the //read logon file

How is checking if a (presently undefined) variable is equal to the NULL value giving you any sort of "file detection" ? Surely you don't expect PHP to automagically understand what you meant to do?

Instead, look at using file_exists() to check if a file already exists or not.

4) I don't know....I should have known better. I will do that in the future. I will be adding automagically to the fun section of my vocab though.

Seems like your logic could be optimized to make the code easier to understand as well as more efficient.

5) Yes i realize this, I will be revising this code much, as its my VERY FIRST php project. You will see lots of me.

If you're trying to read an entire file at once, it's often more efficient and a lot easier to simply use file_get_contents().

Likewise, file_put_contents() is often easier than doing an fopen/fwrite/fclose series.

6) Noted. I will be researching this.

Why do you have a double dollar sign on line #18 of your code snippet above? This should be generating error messages, so either you're ignoring them (why?!) or you don't have a very good development environment (e.g. display_errors set to On and error_reporting set to E_ALL).

7) Yes. After posting my code I fiddled with it some more, it displayed that error, and i removed the duplicate dollar sign.

Your code is technically vulnerable to a race condition, but I'd be more worried about the efficiency/consistency of the way you're storing/handling data.

8) Hmm What do you mean by this? Like unauthorized access?

In other words, why not use a database?

Could you please point me to a tutorial or something that shows me how to properly read and write to a database, securely?