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Working with Files in PHP

Iain Tench(http://www.sitepoint.com/author/itench/)

April 23, 2012

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You may well be familiar with databases such as MySQL and Access which are an everincreasingly common means of storing data. But data

is also stored in files, like Word documents, event logs, spreadsheets, image files, and so on. Databases generally require a special query

language to retrieve information, whereas files are ‘flat’ and usually appear as a stream of text.

Most often when working with files you’ll read from or write to them. When you want to read the contents of a file you first have to open it, then

read as much of the contents as you want, then close the file when you’re finished. When writing to a file, it also needs to be opened (or

perhaps created if it doesn’t already exist), then you write your data to it, and close the file when you have finished. In PHP5 there are some

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builtin wrapper functions that handle the opening and closing automatically for you, but it still happens under the hood.

You may also find it useful to find out more about the file by examining its attributes before you start working with it. For example, does the file

exist? When was it last updated? When was it created?

PHP provides a range of functions which allow you to work with files, and in this article I’ll demonstrate some of them for you.

File Attributes

File attributes are the properties of a file, for example its size, the last time it was accessed, its owner, etc. Let’s look at how you find out more

about the files you’re working with.

File Size

The function filesize() retrieves the size of the file in bytes.

<?php

$f = "C:\Windows\win.ini";

$size = filesize($f);

echo $f . " is " . $size . " bytes.";

When executed, the example code displays:

C:Windowswin.ini is 510 bytes.

The use of a file on a Windows system here highlights an important point; because the backslash has special meaning as an escape character

in strings, you’ll need to escape it by adding another backslash.

If the file doesn’t exist, the filesize() function will return false and emit an E_WARNING , so it’s better to check first whether the file exists

using the function file_exists() :

<?php

$f = "C:\Windows\win.ini";

if (file_exists($f)) {

$size = filesize($f);

echo $f . " is " . $size . " bytes.";

}

else {

echo $f . " does not exist.";

}

In fact many of the functions presented in this section have the same behavior, i.e., emit warnings. I’ve not included a check with

file_exists() in the rest of my examples for the sake of brevity, but you’ll want to use it when you write your own code.

File History

To determine when a file was last accessed, modified, or changed, you can use the following functions respectively: fileatime() ,

filemtime() , and filectime() .

<?php

$dateFormat = "D d M Y g:i A";

$atime = fileatime($f);

$mtime = filemtime($f);

$ctime = filectime($f);

echo $f . " was accessed on " . date($dateFormat, $atime) . ". ";

echo $f . " was modified on " . date($dateFormat, $mtime) . ". ";

echo $f . " was changed on " . date($dateFormat, $ctime) . ".";

The code here retrieves the timestamp of the last access, modify, and change dates and displays them,

C:Windowswin.ini was accessed on Tue 14 Jul 2009 4:34 AM.

C:Windowswin.ini was modified on Fri 08 Jul 2011 2:03 PM.

C:Windowswin.ini was changed on Tue 14 Jul 2009 4:34 AM.

To clarify, filemtime() returns the time when the contents of the file was last modified, and filectime() returns the time when information

associated with the file, such as access permissions or file ownership, was changed.

The date() function was used to format the Unix timestamp returned by the file*time() functions. Refer to the documentation for the dat

e() function (http://php.net/manual/en/function.date.php) for more formatting options.

File Permissions

Before working with a file you may want to check whether it is readable or writeable to the process. For this you’ll use the functions

is_readable() and is_writeable() :

<?php

echo $f . (is_readable($f) ? " is" : " is not") . " readable. ";

echo $f . (is_writable($f) ? " is" : " is not") . " writeable.";

Both functions return a Boolean value whether the operation can be performed on the file. Using the ternary operator you can tailor the display

to state whether the file is or is not accessible as appropriate.

C:Windowswin.ini is readable.

C:Windowswin.ini is not writeable.

File or Not?

To make absolutely sure that you’re dealing with a file you can use the is_file() function. is_dir() is the counterpart to check if it is a

directory.

<?php

echo $f . (is_file($f) ? " is" : " is not") . " a file. ";

echo $f . (is_dir($f) ? " is" : " is not") . " a directory.";

The example code outputs:

C:Windowswin.ini is a file.

C:Windowswin.ini is not a directory.

Reading Files

The previous section showed how you can find out a good deal about the files you’re working with before you start reading or writing to them.

Now let’s look at how you can read the contents of a file.

The convenience function file_get_contents() will read the entire contents of a file into a variable without the need to open or close the

file yourself. This is handy when the file is relatively small, as you wouldn’t want to read in 1GB of data into memory all at once!

<?php

$f = "c:\windows\win.ini";

$f1 = file_get_contents($f);

echo $f1;

For larger files, or just depending on the needs of your script, it’s may be wiser to handle the details yourself. This is because once a file is

opened you can seek to a specific offset within it and read as little or as much data as you want at a time.

The function fopen() is used to open the file:

<?php

$f = "c:\windows\win.ini";

$f1 = fopen($f, "r");

Using the function fopen() , two arguments are needed – the file I want to open and the mode, which in this case is “r” for read. The function

returns a handle or stream to the file, stored in the variable $f1 , which you use in all subsequent commands when working with the file.

The most common mode values are:

For other values, refer to the list in PHP’s fopen() page (http://php.net/manual/en/function.fopen.php).

To read from the opened file one line at a time, use the function fgets() :

<?php

$f = "c:\windows\win.ini";

$f1 = fopen($f, "r");

do {

echo fgets($f1) . " ";

}

while (!feof($f1));

fclose($f1);

Using a do – while loop is a good option because you may not know in advance how many lines are in the file. The function feof() checks

whether the file has reached its end – the loop continues until the end of file condition is reached.

To tidy up after I’ve finished reading the file, the function fclose() is used to close the file.

Writing Files

Two commonly used modes when writing to a file using the function fwrite() are “w” and “a” – “w” indicates you want to write to the file but it

will remove any of the existing file contents beforehand, while “a” means that you will append any new data to what already exists in the file.

You need to be sure you are using the correct option!

In this example I’ll use “a” to append:

<?php

$file = "add_emp.txt";

$f1 = fopen($file, "a");

$output = "banana" . PHP_EOL;

fwrite($f1, $output);

$output = "cheese" . PHP_EOL;

fwrite($f1, $output);

fclose($f1);

First the file name is assigned to a variable, then the file is opened in mode “a” for append. The data to be written is assigned to a variable,

$output , and fwrite() adds the data to the file. The process is repeated to add another line, then the file is closed using fclose() . The

predefined constant PHP_EOL adds the newline character specific to the platform PHP is running on.

The file contents after executing the above code should look like this:

banana

cheese

The convenience function file_put_contents() can also write to a file. It accepts the file name, the data to be written to the file, and the

constant FILE_APPEND if it should append the data (it will overwrite the file’s contents by default).

Here’s the same example as above, but this time using file_put_contents() :

<?php

$file = "add_emp.txt";

file_put_contents($file, "banana" . PHP_EOL);

file_put_contents($file, "cheese" . PHP_EOL, FILE_APPEND);

Working with CSV Files

CSV stands for comma separated variable and indicates the file contains data delimited with a comma. Each line is a record, and each record

is made up of fields, very much like a spreadsheet. In fact, software such as Excel provides the means to save files in this format. Here is an

example as displayed in Excel 2007 (which doesn’t show the commas):

There are 4 lines of data, or records, in the file containing first name, last name, age and job title. To read the file and extract the individual

fields, start by opening the file in read mode:

<?php

$file = "employees.csv";

$f = fopen($file, "r");

Now I need to use a function specifically to read the CSV formatted file, fgetcsv() ; a while loop is used to cater for the fact that the number

of records is expected to vary:

<?php

$file = "employees.csv";

$f = fopen($file, "r");

while ($record = fgetcsv($f)) {

foreach($record as $field) {

echo $field . " ";

}

fclose($f);

This will produce output with a field on each line:

Fred

Smith

Engineer

Susan

Brown

Programmer

Williams

Trainee

Edwards

Analyst

Let’s examine the loop. First, fgetcsv() has one argument only – the file handle; the comma delimiter is assumed. fgetcsv() returns data

in an array which is then processed using a foreach loop. When all records have been read the file is closed using fclose() .

Let’s now look at how you can update or write to a CSV file, this time using the function fputcsv() . Because I am using the same file that I

used above, I will open it in append mode, and the data to be added to the file has been defined in an array.

<?php

$file = "employees.csv";

$f = fopen($file, "a");

$newFields = array(

array('Tom', 'Jones', 36, 'Accountant'),

array('Freda', 'Williams', 45, 'Analyst'),

array('Brenda', 'Collins', 34, 'Engineer'));

foreach($newFields as $fields) {

fputcsv($f, $fields);

}

fclose($f);

The contents of the file as displayed in Excel now look like this:

Summary

This article has given you an introduction into working with files and shown how you can find information about files, read from and write to

files. There are many other functions you can use when working with files – this article has covered some of the most commonly used. You’ll

find more information on PHP’s file system functions page (http://php.net/manual/en/ref.filesystem.php).

Image via Marco Rullkoetter (http://www.shutterstock.com/gallery172795p1.html) / Shutterstock (http://www.shutterstock.com)

Tags: Beginner (http://www.sitepoint.com/tag/beginner/)

Was this helpful?

 

Iain Tench (http://www.sitepoint.com/author/itench/)

Iain Tench has worked in the IT industry for 30 years as a programmer, project manager (Prince2 Practitioner), consultant, and teacher.

As a project manager, he specialized in integration projects mainly involving payment systems in the financial sector. He now teaches

and has acquired a Masters degree in Internet Systems Development as well as a teaching qualification. Iain's specialized areas of

teaching is web technologies, mainly programming in a variety of languages, HTML, CSS and database integration. He's also written a

book about Dreamweaver CS3 for Hodder Education.

Comments for this thread are now closed.

13 Comments

SitePoint

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Kiash • 3 years ago

Is there any way to working with DOC file using PHP?

•

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△▽

Kedar • 3 years ago

What about File Uploading?

•

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nice work! • 3 years ago

but i can open only windows directory, what to do for reading other file of other directory

•

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asad_pk • 4 years ago

Working with CSV Files example is very nice .Thanks

•

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ChonUnca • 4 years ago

would be more interesting if the "write file" section talk about offset, because it's the most complicated part and the less documented. How to insert

a line between 2 others, or insert some chars in a line?

I'd hair teared my self for a long time before understood how it worked.

•

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Mikael Randy • 4 years ago

We are in 2012, PHP current version is 5.4.

From PHP 5.1 (2005 ! 7 years ago !), we ca use the incredible SPL (http://www.php.net/manual/en/b... and especially files handling classes

(http://fr.php.net/manual/en/sp....

But what the hell with theses developers who continue to use these functions from another time?

•

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overcooked

> Mikael Randy

• 3 years ago

For anyone interested in SPL, a good introduction:

http://www.phpro.org/tutorials...

•

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Jason Knight

> Mikael Randy

• 4 years ago

Oh, you want to see just how malfing stupid the SPL documentation is? Look no further than 'appendIterator'.

... and I quote:

"An Iterator that iterates over several iterators one after the other."

With documentation like that, is it any wonder nobody even BOTHERS with SPL?

•

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Jason Knight

> Mikael Randy

• 4 years ago

Lizzyfin has it right in terms of SPL it's so poorly documented I'd be shocked to find anyone who can figure out how it works or even what

it's for.

Just listing methods and parameters does nothing if you don't say what those methods actually DO! Which NONE of the pages in SPL's

docs even come close to!

Of course it's inflated memory use compared to the 'old' procedural methods makes SPL a poor choice in memory restricted environments.

That said, I do get the feeling people are diving for the databases a little too quickly these days. Take a look at the old 'YaBB' board system,

which while not as versatile as it's SQL driven counterparts, is quite often many times faster, and it's certainly easier to move across

servers. There's a reason it's what ProBoards runs under the hood and it's entirely file driven. (in Perl).

My own 'poor mans' system I'm running under a few of my websites is file driven; the news articles have the date encoded in the filename

so I can sort by date off name; then I sort ones of the same date by 'last modified'. It's quick, simple, and more than enough for static pages

or simple news items.

•

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LizzyFin

> Mikael Randy

• 4 years ago

Mikael There's quite a lack of user contributed notes on the PHP pages that you shared and maybe that's why SPL isn't widely

known/used. Certainly, a beginner PHP developer (this tut was categorized for beginners!) would have difficulty with those SPL pages.

Maybe you'd like to share your grand knowledge about SPL with us! Write your own tut instead of whacking down someone else who has

been helpful. Why do you care if another developer chooses the "simple" or an older way of getting things done?

The basic file operations that were reviewed in this tut are simple and easy to understand. I find nothing wrong with using them and

explaining the proper way to use them to other developers. Thanks, Iain!

•

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Frédéric

> Mikael Randy

• 4 years ago

I agree !!

△▽△▽△▽△▽△▽△▽△▽△▽△▽△▽

•

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Ignatius Teo • 4 years ago

Iain, you can also use / as a directory separator in Windows. If you omit the drive spec, the current drive (where the script is running from) is

assumed.

•

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umpirsky

> Ignatius Teo

• 4 years ago

DIRECTORY_SEPARATOR http://php.net/manual/en/dir.c...

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