The default error handling in PHP is very simple. An error message with filename, line number and
a message describing the error is sent to the browser.
When creating scripts and web applications, error handling is an important part. If your code
lacks error checking code, your program may look very unprofessional and you may be open to
This tutorial contains some of the most common error checking methods in PHP.
We will show different error handling methods:
The first example shows a simple script that opens a text file:
If the file does not exist you might get an error like this:
To avoid that the user gets an error message like the one above, we test if the file exist before
we try to access it:
Now if the file does not exist you get an error like this:
The code above is more efficient than the earlier code, because it uses a simple error handling
mechanism to stop the script after the error.
However, simply stopping the script is not always the right way to go. Let's take a look at
alternative PHP functions for handling errors.
Creating a custom error handler is quite simple. We simply create a special function that can be
called when an error occurs in PHP.
This function must be able to handle a minimum of two parameters (error level and error message)
but can accept up to five parameters (optionally: file, line-number, and the error context):
These error report levels are the different types of error the user-defined error handler can be
Now lets create a function to handle errors:
The code above is a simple error handling function. When it is triggered, it gets the error level
and an error message. It then outputs the error level and message and terminates the script.
Now that we have created an error handling function we need to decide when it should be
The default error handler for PHP is the built in error handler. We are going to make the
function above the default error handler for the duration of the script.
It is possible to change the error handler to apply for only some errors, that way the script can
handle different errors in different ways. However, in this example we are going to use our
custom error handler for all errors:
Since we want our custom function to handle all errors, the set_error_handler() only needed one
parameter, a second parameter could be added to specify an error level.
Testing the error handler by trying to output variable that does not exist:
The output of the code above should be something like this:
In a script where users can input data it is useful to trigger errors when an illegal input
occurs. In PHP, this is done by the trigger_error() function.
In this example an error occurs if the "test" variable is bigger than
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.
Possible error types:
In this example an E_USER_WARNING occurs if the "test" variable is bigger than "1".
If an E_USER_WARNING occurs we will use our custom error handler and end the script:
Now that we have learned to create our own errors and how to trigger them, lets take a look at
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
In the example below we will send an e-mail with an error message and end the script, if a
specific error occurs:
And the mail received from the code above looks like this:
This should not be used with all errors. Regular errors should be logged on the server using the
default PHP logging system.
Your Query was successfully sent!