Building A Generic Error Reporting Class In PHP - Raising An Alarm (
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Next, the real meat of this class - the method used to
raise errors and add them to the error stack:
<?php
class errorReporter
{
// manually raise an error
function raiseError($subtype=NULL,
$data="No additional
information
available")
{
$this->_errors[] = array("subtype"
=> $subtype, "data"
=> $data);
if ($this->_getErrorType($subtype) < 1000)
{
//
fatal
$this->displayFatalError($subtype, $data);
}
return $this->_errors;
}
//
snip
}
The raiseError() method is invoked by the developer whenever a need arises to
capture an error in a script; it must be sent an error code identifying the error
type, together with an optional explanatory message or debug data. The error thus
raised is added to the $_errors array, for further processing as and when needed.
In the event that the error raised is a fatal error, the raiseError() class also
invokes the displayFatalError() method. The determination of whether or not an
error is fatal is handled by the _getErrorType() private method, which merely
checks the error code to see if it's above or below 1000.
<?php
class errorReporter
{
// internal function to map subtype to primary
type
function _getErrorType($subtype)
{
return floor($subtype/10)*10;
}
//
snip
}
If an error is fatal, the displayFatalError() method is invoked. Here's what
it looks like:
<?php
class errorReporter
{
// fatal error handler
// clear previously-drawn
screen
// display error template with message
// stop script processing and
die()
function displayFatalError($subtype, $data)
{
ob_clean();
$errorType
=
$this->_errorTypes[$this->_getErrorType($subtype)];
$errorCode = $subtype;
$errorMsg
= $this->_errorsubTypes[$subtype];
$addInfo = $data;
include("error-fatal.php");
die;
}
//
snip
}
This method receives the error code and debug data as input, and has to perform
a number of important tasks.
- First, it needs to clear the output buffer of all previously generated content,
so as to avoid the mangled screen I showed you near the beginning of this article.
In order to do this, it uses the ob_clean() function discussed previously.
- Next, it needs to display an error template, and insert appropriate content into
it reflecting the nature of the error. Using the error code passed to it as argument,
this function looks up the $_errorsubTypes array defined at the top of the class,
and maps the error code to the corresponding human-readable error message. This
data is then inserted into the error template, which contains placeholders for
the error type, error message and debug data and takes care of providing the consistent
error handling earlier stated as one of the design goals for this class.
- Finally, once the error screen has been displayed, it has to terminate further
script processing via a call to die().
The error template to be displayed here is contained within a separate file,
named "error-fatal.php", and include()-d where needed by displayFatalError().
This template can be customized to your specific requirements - here's my bare-bones
version:
<html>
<head>
<basefont face="Arial">
</head>
<body>
<p>
<p>
<table width="100%" border="0" cellspacing="0" cellpadding="5"
bgcolor="Navy">
<tr>
<td bgcolor="Navy" width="100%"><font
color="white"><b>Error!</b></font></td>
</tr>
</table>
<p>
The
following fatal error occurred:
<p>
<b><?=$errorType?> (error code
<?=$errorCode?>)</b>
<br>
<?=$errorMsg?> (<?=$addInfo?>)
</body>
</html>
Wanna see how it works? Here's an example of how you could use the errorReporter
in a script to trap fatal errors,
<?php
// include class
include_once("errorReporter.class.php");
// initialize
error reporter
$e = new errorReporter();
echo "Beginning work...";
// write
to file
$filename = "data.txt";
$fd = fopen ($filename, "wb") or $e->raiseError(208,
$filename); $ret =
fwrite ($fd, "aloha!") or $e->raiseError(207, $filename);
fclose
($fd);
// zero errors?
// display success code
echo "Success!";
?>
and here's an example of the error screen displayed if an error occurs during
script execution:
Note the manner in which the output generated by the script above is first cleared
from the output buffer by the errorReporter class, and is then completely replaced
with the template containing an appropriate error message. No more mangled screens,
no more confused users!
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