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This is the first article in quite a series I want to write. I've thought a while before starting to write to create some kind of plan for me, so I can cover allot of different aspects of PHP. Simultaneously to this series, about PHP, I'm working on a rather large article about setting up Apache with PHP support. PHP with MySQL, Sybase-CT, GD, BCMath, IMAP and more support. Apache with mod_perl, mod_SSL, mod_jserv and more support. As you can see, this is going to be a rather long article once it's finished and I've written all my comments to everything, but I hope it'll be worth the waiting!
Anyways, here's the first article of my series. This one is intended for beginners to PHP, so I'll comment about every line of code there is, for the more advanced user, this may or may not be useful. I'll be glad if at least one person reads this article and finds it useful :)
One more thing to add, all the articles I'm writing are based upon Linux with apache as web server, the articles
themselves are written under windows. If you have a windows-based web server, I can't guarantee for anything. Furthermore, everything is provided on an as-is basis, so don't come cry to me if you crashed your box which was up for 1000days and then crashed simply because you used one of my snippets... what I want to say, use the snippets if you can use them, send me some email if you think they're useful, or if you find a mistake or something, but don't blame me if they don't work on your box. I've tested all of them before I published them, and they worked for me.
Topic: A simple text file based counter
Skill level: newbies
Counters are always nice to have on your web page, so you have an approximate value of how many persons visited your web page. So what does a counter do? It simply increments a value each time someone enters your homepage, nothing more, nothing less (well, there are more advanced counters with statistic usages and and and, but more about this in another article). For this to work, the counter needs to store the number of page views somewhere, e.g.. in a text file. In PHP there are allot of file functions, that's why this is going to be rather easy.
What the script will do: First it will check if the file where the visits are stored already exists. If it does, it reads the number from the file, and writes it back. If the file on the other hand doesn't exist, it will be created with an initial value of 1 page view. But this doesn't display anything yet, so we need to tell the page display the value it stored to the file. Achieving this is pretty simple, as we already have the amount of page views stored in a variable (remember, we read the number of page views from the text file and increment it. This requires that we store it to a variable).
Enough theoretical stuff, let's start with the action! |
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1 <?php
2 $counterfile="./counter.txt";
3 if (file_exists($counterfile)) {
4 $fp = fopen("$counterfile","r+");
5 $pageviews = fread ($fp,7);
6 $pageviews++;
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line by line explanation of the first part of the script. The first line tells the web server that this is a PHP script, and not HTML or something else. On the second line, we tell the PHP interpreter which file to use to store the number of page views in. In this case, it's the file counter.txt in the current directory, e.g.. the directory where the script resides. On line number 3 we check whether or not the file exists. If the file exists we open the file on line 4. $fp is the file-handle we'll need for the further operations with the file, r+ opens the file read and writeable. Line 5 then reads the content of the file. Here we need the file handle we used on line 4 to open the file. 7 says that we read 7 bytes from the file, this means your counter may have a maximum value of 9999999. Which should be more than enough. On line 6 we then increment the umber of page views read from the text file. |
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7 rewind($fp);
8 fputs($fp, $pageviews, 7);
9 fclose($fp);
10 } else {
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Now that we have the incremented value, we reset the pointer to point to the beginning of the file on line 7. when we're back on the beginning of the file, we write the incremented value to the file handle, again 7 bytes long. we then close the file, e.g.. write it back to the file system et voila the counter is incremented! |
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11 $fp = fopen("$counterfile","w");
12 $pageviews = 1;
13 fputs($fp, $pageviews, 7);
14 fclose($fp);
15 }
16 echo "this site has been visited $pageviews times!";
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in the lines here, the file doesn't exist (else on line 10 tells us that it doesn't). So we re-create the file, the parameter "w" opens the file for writing only, places the file pointer at the beginning, and creates the file if it doesn't exist. The next lines do the same as above, but we set the number of page views to 1, as it's the first time the script gets started (unless you erased it academically). With the last line we write to the browser the number of page views... pretty simple huh?
Problems that may occur: If you get an error message that the web server is unable to write to the text file, or read it, then you have a permissions problem. You have to make sure that the user as which the web server runs as has enough privileges to write to the dir where you have your text file. A Most common mistake is also that you forget the semicolon to terminate the commands at the end of a line.
I hope that was useful to some new PHP coders, and send me some feedback about it to enacht@horus.ch!
Emanuel Nacht for weberdev.com |
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