Logging processes with PHP

Its sometimes necessary as a developer to log and track data as it is processed either to debug or to keep a simple record of maybe who’s logged in or out of your site. You could easily do this by accessing a MySQL database and adding a row, but you then have to create and maintain that database. So today I’m going to run through the steps to writing and reading a .txt log file.

The Code

In order to write and access our log file we will be using the php functions fopen() fwrite() and fclose(). find below the rules that can be passed to fopen().

NOTE: It’s important that the file permissions for the log file are set so our script can access and modify it.

function log_action($message="") {
			$logfile = 'logs/log.txt';
			$new = file_exists($logfile) ? false : true;
		        if($handle = fopen($logfile, 'a')) { // append
			$timestamp = strftime("%Y-%m-%d %H:%M:%S", time());
		        $content = "{$timestamp} | {$message}\n";
			fwrite($handle, $content);
			fclose($handle);
			if($new) { chmod($logfile, 0755); }
		  } else {

			echo "Could not open log file for writing.";

		  }
	}

Running the function

In a real application situation we could use logging to track certain aspects of an applications process, for example if I had a video upload script that sends a request to an API to encode the video once it’s uploaded, then puts some data in the database, we could log at each stage of the process to check that each stage was completed successfully and that the script didn’t error out.

Below is a very simple example of how to call the function.

$message = 'Posted to the database';
	log_action($message);

Reading our log file

Above is an image example of the code below minus the row highlighting and thumbnails.

Below is a quick method for displaying the contents of our log file. You can see that the data is displayed in a table for readability. in order to get each line of data we use fgets(); which will get each individual row from our log file, then using the PHP explode() function we can save the data in an array so we can then echo it in the individual table cells.

<table border="0" width="960px" cellpadding="4" cellspacing="0" style="font-family:Arial, Helvetica, sans-serif; font-size:14px;" class="pag">
  <tr style="background:#FFFFCC;">
     <td style="border-bottom:3px solid #FFCC99;">Datetime</td>
    <td style="border-bottom:3px solid #FFCC99;">Video Id</td>
    <td style="border-bottom:3px solid #FFCC99;">Stage</td>
    <td style="border-bottom:3px solid #FFCC99;">Status</td>
  </tr>
<?php
$filename = 'logs/log.txt';
$fp = fopen($filename, "r");
if($fp)
{ 

   while(!feof($fp))
   {
      $line = fgets($fp);
$data = explode('|', $line);

  echo '<tr>
     <td style="padding:5px; border-bottom:1px solid #ccc; border-right:1px solid #ccc;"">'.$data[0].'</td>
    <td style="padding:5px; border-bottom:1px solid #ccc; border-right:1px solid #ccc;"">'.$data[1].'</td>
    <td style="padding:5px; border-bottom:1px solid #ccc; border-right:1px solid #ccc;"">'.$data[2].'</td>
    <td style="padding:5px; border-bottom:1px solid #ccc; ">'.$data[3].'</td>
  </tr>';

   }
}
else
{
  echo ' unable to open file for reading ';
}
?>
</table>