PHP Include
A PHP "Include" is a file that is
included into another file. This concept allows you to re-use content throughout your website.
For example, you could have a standard header and footer on every
page of your website. Instead of copying/pasting this code on to every
page, you could simply place your header code into one include file and
your footer code into another include file. Then, on every page, all you
need to do is refer to the header and footer include files. You can do
this either using the
include() function or the
require() function.
There's only a small difference between the include function and the require function. More on that below.
The include() Function
To include a file using the
include() function, you simply call the function (as you would any other function) and insert the file path as a parameter.
Usage Example
The require() Function
Usage of the
require() function is exactly the same as the
include() function - simply call the function and pass the path of the include file.
The difference between the
include() and
require() functions is in the way they handle errors. If the included file can't be located, the
include() function will still display the rest of the page (as well as an error). The
require() function, on the other hand, will simply display an error - it won't display the rest of the page.
Usage Example
PHP Upload File
You can use PHP to allow your users to upload a file to the server.
To allow users to upload a file to the server, you first need to
provide a form for them to specify which file they want to upload. Once
they click the submit button of the form, the action page is called.
This is the page that needs to contain the PHP code to process the
uploaded file.
The Input Form
Before a user can upload a file, you need to provide them with an
interface that allows them to select a file and initiate the upload.
The following code is an example of an input form. There are a couple of important things to note about this code:
- The action attribute points to a .php file. This is the file that will process the uploaded file.
- There is an attribute called enctype, and its value is multipart/form-data.
- One of the input fields has type="file".
The Action Page
Once the user uploads a file, the file is uploaded into a temporary
directory on the server. If you don't move the file it will disappear.
Therefore, your action page needs to move the file to another location
where it can stay as long as you want it to.
Whenever a file is uploaded, you can find out certain information
about the file including its name, type, size, as well as the name of
the temporary file on the server. These details are made available to
you via a PHP array called
$_FILES.
Displaying Details of the Uploaded File
This code simply displays the details of the uploaded file. It
doesn't move the file to another location - we'll get to that next. For
now, you can use this code in conjunction with the above input form to
demonstrate what happens when you upload a file to the server.
Notice the PHP
$_FILES array which contains info about the file. Note that we also divide the file size by 1024 in order to convert it into kb.
(Ignore any carriage returns in this example - each table row should be on one line).
The above code results in something like this:
| Client Filename: | Water lilies.jpg |
| File Type: | image/jpeg |
| File Size: | 81.830078125 Kb |
| Name of Temp File: | C:\WINDOWS\TEMP\php48B2.tmp |
Moving the Temp File
As mentioned, if we want to keep the file on the server, we need to
move it to another location (of our choice). The following code
demonstrates how to move the file from the temporary location.
Checking for Errors
The $_FILES array includes an item for any errors that may result
from the upload. This contains an error code. If there are no errors,
the value is zero (
0 ).
You check this value within an "If" statement. If the value is
greater than zero, you know an error has occurred and you can present a
user friendly message to the user. Otherwise you can processing the
file.
Restricting File Type/Size
Letting your users upload files to your server can be very risky. If
you're not careful, you could get users uploading all sorts of files -
perhaps including harmful executables etc. You could also find one day
that you've run out of disk space because some users have been uploading
enormous files.
You can restrict the file types and file sizes by using an "if"
statement. If the file type and size are acceptable, processing can
continue, otherwise, display a message to the user.
Important Note: This doesn't prevent the temp file from being
created. The file needs uploaded to the server before PHP can find out
the file size and type. This simply prevents the file from being moved
to your "permanent" location - hence the file should disappear and
(hopefully) not become a problem. In any case, I recommend that you
install good anti-virus software before allowing users to upload files
to your server.
PHP File
In the previous lesson we learned how to enable our users to upload
files to the server. In this lesson, we'll learn how to work with files
on the server.
Reading a File
The following code can be used to read a file.
Here's an explanation of what's happening:
- Before you read a file you need to open it. We're using PHP's fopen() function and providing it with two parameters: the file name and the mode in which it should be opened.
- We then loop through the file using PHP's feof() function.
This checks for the end of the file. Our loop specifies that, while the
end of file has not been reached, process the code inside the loop.
- The code inside the loop uses PHP's fgets() function. This
function reads the file line by line. We need to put our own break
otherwise each line would end up on the same line.
- Finally, we close the file using PHP's fclose() function, passing the opened file as a parameter.
Writing to a File
The following code can be used to write to a file.
Here's an explanation of what's happening:
- Again, we use PHP's fopen() function and supply it with two parameters: the file name and the mode in which it should be opened.
- We then use PHP's fwrite() function to write to the file. We supply two parameters: the opened file, and the text to go inside the file.
- Finally, we close the file using PHP's fclose() function, passing the opened file as a parameter.
Appending Data to a File
The previous code overwrites any content that might have been in the
file. If you only want to add to the end of the existing data, you can
simply change the mode from "w" (for "write") to "a" (for "append").
Deleting a File
To delete a file, you use PHP's
unlink() function and provide it with the name/path of the file to delete.
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