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For 2021 - online Python 3 training - see ((here)).

Our plans were to retire in summer 2020 and see the world, but Coronavirus has lead us into a lot of lockdown programming in Python 3 and PHP 7.
We can now offer tailored online training - small groups, real tutors - works really well for groups of 4 to 14 delegates. Anywhere in the world; course language English.

Please ask about private 'maintenance' training for Python 2, Tcl, Perl, PHP, Lua, etc.
PHP header() function - uses and new restrictions

PHP's header function allows you to change the headers on your returned content so that (examples)

• The browser receives not HTML but plain text, a .jpg image or a file to save locally
   example: header ('Content-type: Application/Octet-stream');

• You can change a "404" missing reponse code into a "200" - good.
   example: header("HTTP/1.1 200 OK");

• You can send out cache instructions
   example: header("cache-control: no-store");

• you can sent out a save file name if you're saving the file.
   example: header ('Content-Disposition: attachment; filename="hello.txt"');

However, up until PHP 4.4.2 / PHP 5.1.2 it was prone to injection attacks. If you used a variable within the parameter and your user could set that variable to include a new line character, he could add in any other header at all.

As from the releases above, you should send separate header directives if you want to set multiple headers as PHP has been altered to take care of the potential security issue and is not backwards compatible over this.

There's an example in our "database download to local CSV file" demonstration with required to set both a content-type and a content-disposition. Have a look at the source code in which I have commented out the old and replaced it by the new. The old was producing a message like:
Warning: Header may not contain more than a single header, new line detected. in C:\Domains[part of URL removed]testsite\phpcsv\phptocsv1.php on line 30

Note also with the header function - you may ONLY call it before your PHP script has sent out any content to the browser. This means that it must be in a block of PHP that comes at the very top of your script (no blank lines or spaces before the initial <?php please). See also the ob_start function which, however, I dislike.
(written 2007-05-30, updated 2007-06-07)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
H112 - PHP - Further Web Page and Network Handling
  [220] When to use Frames - (2005-02-19)
  [314] What language is this written in? - (2005-05-17)
  [345] Spotting a denial of service attack - (2005-06-12)
  [356] Sudoku helper or sudoku cheat - (2005-06-23)
  [372] Time calculation in PHP - (2005-07-08)
  [376] What brings people to my web site? - (2005-07-13)
  [410] Reading a news or blog feed (RSS) in your PHP page - (2005-08-12)
  [425] Caching an XML feed - (2005-08-26)
  [443] Server side scripting of styles to suit the browser - (2005-09-12)
  [451] Accessing a page via POST from within a PHP script - (2005-09-26)
  [484] Setting the file name for a downloaded document - (2005-11-03)
  [537] Daily Image Santafied - (2005-12-22)
  [542] Morning image, afternoon image - (2005-12-26)
  [565] Using PHP to output images, XML, Style sheets, etc - (2006-01-15)
  [603] PHP - setting sort order with an associative array - (2006-02-13)
  [675] Adding PHP tags to an old cgi program - (2006-04-08)
  [767] Finding the language preference of a web site visitor - (2006-06-18)
  [789] Hot answers in PHP - (2006-07-02)
  [847] Image maps for navigation - a straightforward example - (2006-08-28)
  [904] Of course I'll tell you by email - (2006-10-25)
  [936] Global, Superglobal, Session variables - scope and persistance in PHP - (2006-11-21)
  [1009] Passing GET parameters through Apache mod_rewrite - (2006-12-27)
  [1114] PHP Image upload script - (2007-03-21)
  [1183] Improving searches - from OR to AND? - (2007-05-11)
  [1187] Updating a page strictly every minute (PHP, Perl) - (2007-05-14)
  [1355] .php or .html extension? Morally Static Pages - (2007-09-17)
  [1379] Simple page password protection - PHP - (2007-10-04)
  [1485] Copyright and theft of images, bandwidth and members. - (2007-12-26)
  [1495] Single login and single threaded models - Java and PHP - (2008-01-04)
  [1496] PHP / Web 2 logging - (2008-01-06)
  [1505] Script to present commonly used images - PHP - (2008-01-13)
  [1515] Keeping staff up to date on hotel room status - (2008-01-22)
  [1518] Downloading data for use in Excel (from PHP / MySQL) - (2008-01-25)
  [1549] http, https and ajp - comparison and choice - (2008-02-22)
  [2632] Shipping a test harness with your class in PHP - (2010-02-12)
  [2679] How to build a test harness into your PHP - (2010-03-16)
  [2729] Uploading a document or image to its own URL via a browser - (2010-04-18)
  [2918] Downloading a report from the web for further local analysis - (2010-08-13)
  [3036] Sending out an email containing HTML from within a PHP page - (2010-11-07)
  [3432] 3 digit HTTP status codes - what are they, which are most common, which should be a concern? - (2011-09-11)
  [3540] Easy session example in PHP - keeping each customers data apart - (2011-12-06)
  [3568] Telling which ServerAlias your visitor used - useful during merging domains - (2012-01-04)
  [3918] Multiple page web applications - maintaining state - PHP - (2012-11-10)
  [4070] Passing variable between PHP pages - hidden fields, cookies and sessions - (2013-04-26)
  [4483] Moving from mysql to mysqli - simple worked example - (2015-05-03)


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Some other Articles
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MySQL - the order of clauses and the order of actions
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A lot has happened in a year
PHP header() function - uses and new restrictions
Where did the Bank Holiday go?
Meet other local businesses in Melksham
Simple but effective use of mod_rewrite (Apache httpd)
Where and When - can you place the picture?
Arrival and Departure experiences - another hotel
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This is a page archived from The Horse's Mouth at http://www.wellho.net/horse/ - the diary and writings of Graham Ellis. Every attempt was made to provide current information at the time the page was written, but things do move forward in our business - new software releases, price changes, new techniques. Please check back via our main site for current courses, prices, versions, etc - any mention of a price in "The Horse's Mouth" cannot be taken as an offer to supply at that price.

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