Strings and PHP

If you read the 'PHP Hypertext Preprocessor' column, you might have been wondering about some of the peculiarities of string handling with PHP. Strings, simply, consist of one or more characters in sequence. In PHP, $s = "string" creates a string variable 's' that contains the string "string".

Python vs. PHP: Choosing your next project's language

What about the more complicated strings in last month's example? One string was "The time is ".date('D M d H:i:s T Y')."\n"; in fact, this is three sub-strings.

How does this work? PHP allows you to append strings to other strings using the '.' (full stop) character. When the PHP script gets executed and our example above runs, PHP reads it as follows: build a string from the text "The time is", append the results of a call to the date() function, then append '\n' (a new line) to that. This can be really useful when your programs get information from several sources and you need to collate it.

Interacting with files

One of the best applications for PHP is delivering content stored in files or databases. In the first case, PHP makes available a range of functions to use when interacting with files (see for a complete list). One of the easiest ways to retrieve data from a file with PHP is to use the function fpassthru(); an example follows. First, put some random text into a file and call it 'data.txt'. Then create this script:

$fp = fopen("data.txt","r");
Save the script as fpassthru.php in the same directory as data.txt on your PHP-enabled Web server (for PHP 4 and Apache Web server software and installation details, see the cover CD). Requesting the page from your Web server will give you the contents of the file in an HTML document.

How does this work? The fopen() function opens the file data.txt for reading at the beginning of the file (you can open files in other modes; find a full list at

The fopen() function returns a file pointer, which is a variable needed to tell the other file system functions which file you wish to manipulate. In our example, we supply fpassthru() with the file pointer for data.txt. As its name suggests, fpassthru() reads each line from the file, and outputs it. Notice that we do not need to close the file; fpassthru() does that.

Another way to replicate the functionality of fpassthru, but to have more control over what is read from the file, is to use fgets(). This function returns a line, or a portion thereof, as a string and moves the current position in the file forward one line. For example, when you call fopen() in read mode, the current position is set to the first line. By calling fgets($fp,100), the first 100 characters of the file pointed to by $fp are returned (or the whole line if that line is fewer than 100 characters long), and the current position in the file is set to the second line. To see what this allows us to do, replace the call to fpassthru() with the following:

while(!feof($fp)) { echo "Line $i: ".fgets($fp,1024); $i++; } fclose($fp);

Save this as fgets.php and request it from your Web server. You will see each line of your data.txt file displayed on the line number on the left margin.

New features

fgets.php introduces some new aspects of PHP. One is the while loop, which continues to execute the code inside its curly braces - { } - while the argument to while() remains true.

Like most programming languages, PHP is based on bivalent evaluation - truth and falsity. In PHP, the value 0 denotes the latter, and any other value the former. The bang (or exclamation mark) reverses the truth or falsity of the expression following it. For example, !1, !-1, !1234 are all false, while !0 is true. The bang is used in fgets.php to reverse the value returned by feof() - a function that indicates if the current file position is the end of the file. So, the while loop condition reads 'loop while the current line is not the end of the file'.

The last new feature of PHP revealed in fgets.php is that of incrimination. The line $i++ is equivalent to $i = $i + 1. The '++' simply means 'increment by one'.

There are many other ways to read data from files with PHP, exploration of which is left as an exercise.

Join the newsletter!

Error: Please check your email address.
Rocket to Success - Your 10 Tips for Smarter ERP System Selection
Keep up with the latest tech news, reviews and previews by subscribing to the Good Gear Guide newsletter.

Gavin Sherry

PC World
Show Comments



Victorinox Werks Professional Executive 17 Laptop Case

Learn more >

Sansai 6-Outlet Power Board + 4-Port USB Charging Station

Learn more >



Back To Business Guide

Click for more ›

Brand Post

Most Popular Reviews

Latest Articles


PCW Evaluation Team

Louise Coady

Brother MFC-L9570CDW Multifunction Printer

The printer was convenient, produced clear and vibrant images and was very easy to use

Edwina Hargreaves

WD My Cloud Home

I would recommend this device for families and small businesses who want one safe place to store all their important digital content and a way to easily share it with friends, family, business partners, or customers.

Walid Mikhael

Brother QL-820NWB Professional Label Printer

It’s easy to set up, it’s compact and quiet when printing and to top if off, the print quality is excellent. This is hands down the best printer I’ve used for printing labels.

Ben Ramsden

Sharp PN-40TC1 Huddle Board

Brainstorming, innovation, problem solving, and negotiation have all become much more productive and valuable if people can easily collaborate in real time with minimal friction.

Sarah Ieroianni

Brother QL-820NWB Professional Label Printer

The print quality also does not disappoint, it’s clear, bold, doesn’t smudge and the text is perfectly sized.

Ratchada Dunn

Sharp PN-40TC1 Huddle Board

The Huddle Board’s built in program; Sharp Touch Viewing software allows us to easily manipulate and edit our documents (jpegs and PDFs) all at the same time on the dashboard.

Featured Content

Product Launch Showcase

Latest Jobs

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?