Error Handling

die() Function

The example below shows a simple script that opens a text file:


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If the "file.txt" file does not exist, you might get an error like this:


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To avoid that the user gets an error message like the above, we test if the file exist before we try to access it:


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Custom Error Handler

It is quite simple to create a custom error handler, just by creating a function that can be called when an error occurs, and the function must be able to handle at least 2 parameters (error level & error message). The function also can accept up to 5 parameters. Please look at the description below:

Syntax:



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Error Report Level


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Let we try to create a function to handle errors:


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When the function above is triggered, it gets the error level and an error message. It then outputs the error level and message, and then it will terminates the script.



Set Error Handler


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Now, let we try testing the error handler by trying to output variable that does not exist:


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############################################################
The Output:

Error: [8] Undefined variable: var
############################################################



Trigger an Error

You can trigger an error when users input the illegal data. In PHP, we will use the trigger_error() function:


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And the output should be something like this:

############################################################
Notice: Value must be 5 or below
in C:\webfolder\index.php on line 7
############################################################

There are several possible error types:

• E_USER_ERROR - Fatal user-generated run-time error. Errors that can not be recovered from. Execution of the script is halte.
• E_USER_WARNING - Non-fatal user-generated run-time warning. Execution of the script is not halte.
• 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 normall.

The example below shows an E_USER_WARNING occurs if the var variable is bigger than 5. If an E_USER_WARNING occurs we will use our custom error handler and end the script:


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And the output should be something like this:

############################################################
Error: [512] Value must be 5 or below
Ending Script
############################################################



Error Logging

You maybe need to send error log to the servers logging system or remote destination, but it depend on how the error_log configuration is set in the php.ini file. In this case, it is the best way if you try to send the error log to yourself to get notified of specific errors. Lets see the code below for example:


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The output should be something like this:

############################################################
Error: [512] Value must be 5 or below
Administrator has been notified
############################################################

And somebody (in this case: yourself) will received mail from the code above looks like this:

############################################################
Error: [512] Value must be 5 or below
############################################################

Uploading File

Form to Upload File

See the example below:


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Here is the description about the HTML code above:

• The enctype attribute of the form tag specifies which content type to use when submitting a form.
• "multipart/form-data" is used when a form requires binary data, like the contents of a file, to be uploaded.
• The type="file" attribute of the input tag specifies that the input should be processed as a file.

Script for Uploading File

The "upload_file.php" file above contains the code for uploading a file:


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The description about the code above:

• $_FILES["file"]["name"] - the name of the uploaded file.
• $_FILES["file"]["type"] - the type of the uploaded file.
• $_FILES["file"]["size"] - the size in bytes of the uploaded file.
• $_FILES["file"]["tmp_name"] - the name of the temporary copy of the file stored on the server.
• $_FILES["file"]["error"] - the error code resulting from the file upload.

Restrictions on Upload

In the script below, we can try to add some restrictions to the file upload by just uploading .gif or .jpeg files and the file size must be under 50 kb:


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Saving the Uploaded File


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File Handling

Opening a File

We will be using fopen() function to open files in PHP: Look at the example below:


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Your file maybe opened in one of the following modes:


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The example below shows a message that is generated if the fopen() function is unable to open the specified file:


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Closing a File

To close an open file, we will use fclose() function:


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