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IF Construct in One Line Using PHP

Dagu — Mon, 14 Sep 2009 03:49:49 +0000

The if construct is one of the most important features of many languages, PHP included. It allows for conditional execution of code fragments. PHP features an if structure that is similar to that of C:

if (expr)
   statement

The general format of if construct is like shown below:

if (expr1) {
   //  statement if expr 1 true
} else if (expr2) {
   // statement if expr 2 true
} else {
   // statement if expr 1 and 2 false
}

You may find useful documentation about if construct, else and else if in php.net.

But how if you only need two condition to produce a word or digit, and then save it into a variable or just echo it? You may write it like shown below:

if ($status = '0')
   echo 'Draft';
else
   echo 'Published';

In code example above, you need to write four lines. Compare with code shown below:

echo $status == '0' ? 'Draft' : 'Published';

The syntax is show below

echo expr ? 'value if true' : 'value if false';

You may change echo with variable assignment such as:

$var = expr ? 'value if true' : 'value if false';

Easy right? It cuts down four lines into one line only.

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Load PHP Extension

Dagu — Mon, 10 Nov 2008 16:19:10 +0000

A few CMSs need PHP library which is not activated as default. For example, in installation an e-commerce named magento (www.magentocommerce.com), needs a few PHP extensions. Usually, a good CMS checks system requirements before installation begins. Image below is an example for system requirements checking on Magento Installation.

System Requirement Checking on Magento Commerce

We could use phpinfo() function to view which extensions have been loaded. The php.ini file is used to configure it. We could find it in PHP installation directory. If you use XAMPP, PHP configuration can be found in [XAMPP's Installation directory]/apache/bin.

To edit it, simply use a text editor (such as notepad). Find which extension will be activated. For example, in magento case, it needs curl and mcrypt extensions to be activated. All we need is finding lines that have words php_curl.dll and php_mcrypt.dll in php.ini. As default, the configuration for those extensions is:

;extension=php_curl.dll
;extension=php_mcrypt.dll

To activate them we need to delete semicolon in the first character of those two lines. If we have done, restart apache and check extensions status using phpinfo().

PHP Info

Question: why does we delete that semicolon?
In PHP configuration file (you will find the same thing in apache configuration), a semicolon is used to mark that the line after that will not be executed. Because of that, the programmers use it to make comments.

Becareful if you need to edit configuration file. If you make a mistake, possibly your PHP won’t work well. Always make a configuration file backup before make changes, in order to make sure it would be easy to restore the configuration file if something wrong happens.

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Avoid Direct Download

Dagu — Wed, 19 Dec 2007 02:29:00 +0000

Case study:
We would like to provide pdf files to be downloaded by visitors, but the file location is hidden. Visitors can download file with URL given only. Programming language used is PHP.

Analysis:
We could make a link directly to the file location. Example:

Download MyEbook

What happen if the link above clicked? It depends to the visitors’ browser. If the plugin to read pdf is installed, then browser will open that file inside browser. But, how if there’s no pdf reader plugin? Then a save file dialog box appear. We could save that file.

A problem is done if the visitors don’t have pdf reader plugin. But what about the visitors who have it? Of course the problem is not solved. Another problem is the visitors know the file location, so it allows the visitors to download the file directly (download it directly by typing/copy paste the URL in the browser, without clicking from link given).

Solution:
We need a bit code (PHP) to solve this problem.

The code to avoid direct download is shown below:

$task = $_REQUEST['task'];

switch($task) {
case 'download':
// file location
$file_path = 'dl/myebook.pdf';
// function to get file name without path
$file_name = basename($file_path);
// get file size
$fsize = filesize($file_path);
// set headers
header("Pragma: public");
header("Expires: 0");
header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
header("Cache-Control: public");
header("Content-Description: File Transfer");
header("Content-Type: application/pdf");
header('Content-Disposition: attachment; filename="' . $file_name . '"');
header("Content-Transfer-Encoding: binary");
header("Content-Length: " . $fsize);
// start downloading from here
$file = @fopen($file_path,"rb");
if ($file) {
while(!feof($file)) {
print(fread($file, 1024*8));
flush();
if (connection_status()!=0) {
@fclose($file);
die();
}
}
@fclose($file);
}
break;
default:
echo 'Download MyEbook';
break;
}

You need to concern to this line:

header('Content-Disposition: attachment; filename="myebook.pdf"');

This line forces browser to show save dialog box for “myebook.pdf” although there’s pdf reader plugin in the browser.

To change file type (exe or zip), we need to change Content-Type only. Here are the lists:

// archives
application/zip

// documents
application/pdf
application/msword
application/vnd.ms-excel
application/vnd.ms-powerpoint
// executables
application/octet-stream

// images
image/gif
image/png
image/jpeg

// audio
audio/mpeg
audio/x-wav

// video
video/mpeg
video/quicktime
video/x-msvideo

File starts downloading from the line after this line:

// start downloading from here

There’s a question. Why do we need to avoid direct download? The purpose is to check how many times a file has been downloaded. If the visitors are allowed to download files directly, I’m sure it will be difficult to know how many times a file is downloaded. If you don’t need to check how many times the visitors download your files, you could use both direct download or indirect download.

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