HomePHP Page 5 - File And Directory Manipulation In PHP (part 1)
Weather Balloon - PHP
PHP comes with a powerful and flexible file manipulation API that allows developers (among other things) to read and write files, view and modify file attributes, read and list directory contents, alter file permissions, and retrieve file contents into a variety of native data structures. Find out more, inside.
Let's consider some more realistic examples. This next piece of code connects to a MySQL database, retrieves a result set and either displays it in a browser or writes it to a file based on a configuration variable.
<?php
// user-defined output handler
function myOutputHandler($buf)
{
global $output;
// either dump the buffer to a file
if ($output != "www")
{
$fp = fopen ("weather.html", "w");
fwrite($fp, $buf);
fclose($fp);
}
// ... or return it for printing to the browser
else
{
return $buf;
}
}
// start buffering the output
// specify the callback function
ob_start("myOutputHandler");
// output format - either "www" or "file"
$output = "www";
<?
// open connection to database
$connection = mysql_connect("localhost", "joe", "nfg84m")
or die ("Unable to connect!");
mysql_select_db("weather") or die ("Unable to select database!");
// get data
$query = "SELECT * FROM weather";
$result = mysql_query($query) or die ("Error in query: $query. " .
mysql_error());
// if a result is returned
if (mysql_num_rows($result) > 0)
{
// iterate through resultset
// print data
while (list($temp, $forecast) = mysql_fetch_row($result))
{
echo "Outside temperature is $temp";
echo "<br>";
echo "Forecast is $forecast";
echo "<p>";
}
}
else
{
echo "No data available";
}
// close database connection
mysql_close($connection);
// send some more output
?>
</body>
</html>
<?php
// end buffering
// this will invoke the user-defined callback
ob_end_flush();
?>
This example uses PHP's output buffering functions to create a custom output buffer handler. When ob_end_flush() is called, PHP will invoke the user-defined function myOutputHandler(), and will pass the entire contents of the buffer to it as a string. It is now up to the function to decide what to do with the buffer - either print it to the Web browser or write it to a static HTML file for later use.
Sometimes, overwriting file contents is not exactly what you need - in some cases, what you really want to do is append to an existing file. This is common when dealing with log files, as in the example below:
<?php
// set log file
function writeLog($msg)
{
// set file to write
$filename = "error.log";
// open file
$fh = fopen($filename, "a") or die("Could not open log");
// create the data string to be written
$str = date("[Y-m-d h:i:s] ", mktime()) . $msg . "\r\n";
// write to log
fwrite($fh, $str) or die("Could not write to log");
// open connection to database
$connection = mysql_connect("localhost", "joe", "nfg84m")
or
writeLog("FATAL: Unable to connect!");
mysql_select_db("weather") or writeLog("FATAL: Unable to select
database!");
// get data
$query = "SELECT * FROM books";
$result = mysql_query($query) or writeLog("FATAL: Error in query: $query.
" . mysql_error());
// if a result is returned
if (mysql_num_rows($result) > 0)
{
// iterate through resultset
// print data
while (list($title, $author) = mysql_fetch_row($result))
{
echo "$title - $author <br>";
}
}
else
{
echo "No data available";
}
// close database connection
mysql_close($connection);
PHP 
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