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Building an Error-Handling Mechanism - Page 3

by: PHP Builder Staff
|
September 9, 2009

An error can be triggered anywhere you wish in a script, and by adding a second parameter, you can specify what error level is triggered.
E_USER_ERROR - Fatal user-generated run-time error. Errors that can not be recovered from. Execution of the script is halted
E_USER_WARNING - Non-fatal user-generated run-time warning. Execution of the script is not halted
E_USER_NOTICE - Default. User-generated run-time notice. The script found something that might be an error, but could also happen when running a script normally

In this example an E_USER_WARNING occurs if the "example" variable is greater than 1. If an E_USER_WARNING occurs we will use our custom error handler and end the script.

<?php
//error handler function
function customError($errno, $errstr)
{
echo "Error: [$errno] $errstr";

echo "Ending Script";
die();
}

//set error handler
set_error_handler("customError",E_USER_WARNING);

//trigger error
$example = 2;
if($test > 1)
{
trigger_error("Value must be 1 or below",E_USER_WARNING); }
?>

The output of the code above should be something like this:

Error: [512] Value must be 1 or below
Ending Script

Now that we have learned to create our own errors and how to trigger them, lets take a look at error logging.
By default, PHP sends an error log to the servers logging system or a file, depending on how the error_log configuration is set in the php.ini file. By using the error_log() function you can send error logs to a specified file or a remote destination.
Sending errors messages to yourself by e-mail can be a good way of getting notified of specific errors.
In the example below we will send an e-mail with an error message and end the script, if a specific error occurs: 

<?php 
//error handler function 
function customError($errno, $errstr) 
{ 
    echo "Error: [$errno] $errstr"; 
     echo "Webmaster has been notified"; 
    error_log("Error: [$errno] $errstr",1, 
    "here@there.com","From: website@server.com"); 
} 

//set error handler 
set_error_handler("customError",E_USER_WARNING); 

//trigger error 
$example=2; 
if($example > 1) 
{ 
    trigger_error("Value must be 1 or below",E_USER_WARNING); 
} 
?>

The output of the code above should be something like this:

Error: [512] Value must be 1 or below

Webmaster has been notified

And the mail received from the code above looks like this: 

ERROR: [512] VALUE MUST BE 1 OR BELOW

Conclusion
Something best remembered is that users do not want to see your error messages. They are there for the content. Something important to do is to show them a meaningful notice should that content not be available to them. Above I have shown very technical error reporting, but I think you can find your own balance between what you need to know and what the user needs to see.
Until next time.
Marc Steven Plotz

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