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PHP: File Downloads HTTP Headers

May 16th, 2007 by Pete

In PHP you can provide file downloads by using a PHP page to “pass through” the file. Of course you could just link to the actual file, however this technique means your file can kept outside of your website root. Another advantage is you can integrate this system into a PHP based user/password system easily.

Now this technique is fairly straightforward, but you need to make sure you get the HTTP Headers correct for it to run smoothly. Here’s the code:

PLAIN TEXT
PHP:
  1. $file = "/path/to/file.txt";
  2. $file_extension = strtolower(substr(strrchr($basename,"."),1));
  3.  
  4. //This will set the Content-Type to the appropriate setting for the file
  5. switch ($file_extension)
  6. {
  7. case "htm":
  8. case "xhtml";
  9. case "txt";
  10. case "html": $ctype="text/html"; break;
  11. case "pdf": $ctype="application/pdf"; break;
  12. case "doc": $ctype="application/msword"; break;
  13. case "exe": $ctype="application/octet-stream"; break;
  14. case "zip": $ctype="application/zip"; break;
  15. case "xls": $ctype="application/vnd.ms-excel"; break;
  16. case "ppt": $ctype="application/vnd.ms-powerpoint"; break;
  17. case "gif": $ctype="image/gif"; break;
  18. case "png": $ctype="image/png"; break;
  19. case "jpeg":
  20. case "jpg": $ctype="image/jpeg"; break;
  21. case "mp3": $ctype="audio/mpeg"; break;
  22. case "wav": $ctype="audio/x-wav"; break;
  23. case "mpeg":
  24. case "mpg":
  25. case "mpe": $ctype="video/mpeg"; break;
  26. case "mov": $ctype="video/quicktime"; break;
  27. case "avi": $ctype="video/x-msvideo"; break;
  28. default: $ctype="application/force-download";
  29. }
  30.  
  31. //Begin writing headers
  32. header("Pragma: public");
  33. header("Expires: 0");
  34. header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
  35. header("Cache-Control: public");
  36. header("Content-Description: File Transfer");
  37. //Use the switch-generated Content-Type
  38. header("Content-Type: $ctype");
  39. header("Content-Length: ".filesize($file));
  40.  
  41. // regex stops download prompt for browser associated types
  42. if (!preg_match('/(htm|xhtml|txt|html|gif|png|jpeg|jpg)/', $file_extension, $matches))
  43. header("Content-Disposition: attachment; filename=\"".basename($filename)."\";" );
  44.  
  45. // output the file
  46. readfile("$file");
  47. exit();

I will be writing a follow up article in the future that shows how this technique can be improvement using Apache's mod-rewrite to provide cleaner URLs for file downloads.

Note: The regular expression on line 42 will make files normally associated with the browser (images, webpages, etc) open inside the browser. If you want to get the “open/save” download prompt for all types of files then comment out this line.

Note: Make sure you use: “Content-Type: image/jpeg” for JPGs, IE doesn’t seems to like “Content-Type: image/jpg”

# Pete Graham

Posted in Website Development, php, regular expressions, programming | 2 Comments »

PHP: Get First Index in Associative Array

May 15th, 2007 by Pete

The other day I was programming in PHP and needed to get the first index in an associative array. There doesn’t appear to be a built in function to deal with this so I wrote my own.

PLAIN TEXT
PHP:
  1. function getArrayFirstIndex($arr)
  2. {
  3. foreach ($arr as $key => $value)
  4. return $key;
  5. }

Here's a bit of code you can test it on:

PLAIN TEXT
PHP:
  1. $arr['banana'] = "yellow";
  2. $arr['apple'] = "apple";
  3. $arr['orange'] = "orange";
  4.  
  5. $first_index = getArrayFirstIndex($arr);
  6.  
  7. echo "first index =".$first_index;

The above code will output 'first index = banana'.

/* Pete Graham */

Posted in Website Development, php, programming | 4 Comments »

JS: Execute JavaScript on Page Load

May 14th, 2007 by Pete

Recently I’ve been making an effort to improve my JavaScript skills, I’m not a JavaScript-Jedi yet but I have been picking up a few, tips, tricks and techniques.

One thing that I find extremely useful is using an init function to call other functions when the page has loaded. I have been using the nifty function below:

PLAIN TEXT
JAVASCRIPT:
  1. function WindowOnload(f)
  2. {
  3. var prev=window.onload;
  4. window.onload=function(){ if(prev)prev(); f(); }
  5. }

I save this function in a file called init.js which is then included in my HTML pages using:

PLAIN TEXT
HTML:
  1. <script xsrc="/js/init.js" type="text/javascript"></script>

Functions can then be initialised by including the following in the HTML:

PLAIN TEXT
JAVASCRIPT:
  1. <script language="JavaScript">
  2. <!--
  3.  
  4. WindowOnload(function()
  5. {
  6. a_function('Sdelete_date');
  7. });
  8.  
  9. WindowOnload(function()
  10. {
  11. another_function('a_parameter');
  12. });
  13.  
  14. //-->
  15. </script>

The above code is inline JavaScript which is often seen as being naughty, obviously you can save the same code to a separate file and include that instead.

I originally saw this technique here. Alternative JS initialisation scripts are available but so far this one has worked well for me, so I’ll be sticking with it.

# Pete Graham

Posted in javascript, Website Development, programming | No Comments »

PHP: Swap Variables One Liner

March 29th, 2007 by Pete

Here's a nifty one liner in PHP which let's you swap 2 variables values.

PLAIN TEXT
PHP:
  1. list($a,$b) = array($b,$a);

Much like the PHP XOR swap there's no real reason this is any better than using a temporary variable, but you might be able to impress chicks with it or something.

/* Pete Graham */

Posted in Tech, php, programming | 4 Comments »

PHP: Remove Values from Array

March 22nd, 2007 by Pete

If you need to remove elements from an array that have a particular value(s) here’s a neat way of doing it without any looping:

PLAIN TEXT
PHP:
  1. // our initial array
  2. $arr = Array("blue", "green", "red", "yellow", "green", "orange", "yellow", "indigo", "red");
  3. print_r($arr);
  4.  
  5. // remove the elements who's values are yellow or red
  6. $arr = array_diff($arr, array("yellow", "red"));
  7. print_r($arr);
  8.  
  9. // optionally you could reindex the array
  10. $arr = array_values($arr);
  11. print_r($arr);

This is the output from the code above:
Array ( [0] => blue [1] => green [2] => red [3] => yellow [4] => green [5] => orange [6] => yellow [7] => indigo [8] => red )
Array ( [0] => blue [1] => green [4] => green [5] => orange [7] => indigo )
Array ( [0] => blue [1] => green [2] => green [3] => orange [4] => indigo )

Pete Graham xXx

Posted in Tech, php, arrays, programming | 11 Comments »

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