{"id":164,"date":"2008-06-16T10:18:04","date_gmt":"2008-06-16T18:18:04","guid":{"rendered":"http:\/\/www.oeconomist.com\/blogs\/daniel\/?p=164"},"modified":"2020-11-05T02:14:56","modified_gmt":"2020-11-05T10:14:56","slug":"a-useful-bit-o-php-code","status":"publish","type":"post","link":"https:\/\/www.oeconomist.com\/blogs\/daniel\/?p=164","title":{"rendered":"A Useful Bit o' PHP Code, Set Right"},"content":{"rendered":"

I came upon someone's ancient 'blog entry in which he or she attempted to present what would be a useful PHP function<\/a>. Unfortunately, the code has a few bugs.<\/p>

A dynamic webpage may seek data from various sources, including data passed by GET<\/code> and POST<\/code> methods<\/a> (which is how web forms normally), persistent data in cookies<\/a> (stored on the client but provided to the server with each visit), and persistent data on the server.<\/p>

Towards that end, PHP<\/a> maintains five associative arrays: $_GET<\/code><\/a>, $_POST<\/code><\/a>, $_COOKIE<\/code><\/a>, $_REQUEST<\/code><\/a>, and $_SESSION<\/code><\/a>. ($_REQUEST<\/code><\/a> combines the contents of $_GET<\/code><\/a>, $_POST<\/code><\/a>, and $_COOKIE<\/code><\/a>.) To access a variable named user<\/code><\/q> sent by POST<\/code> method, one would refer to $_POST[\"user\"]<\/code>, and so forth.<\/p>\r\n\r\nThe 'blog entry in question<\/a> may have been written before $_REQUEST<\/code><\/a> was introduced; in any event, the author had two good ideas:

  1. Avoid errors resulting from trying to access variables that don't actually exist. If no variable user<\/code> was passed by POST<\/code>, then $_POST[\"user\"]<\/code> throws an error. To avoid that sort of thing, the author checks for the presence of the variable before attempting to access it.<\/li>
  2. Combine the variables in $_SESSION<\/code><\/a>, as well as those in $_GET<\/code><\/a>, $_POST<\/code><\/a>, and $_COOKIE<\/code><\/a>. Indeed, session data is more analogous to cookie data than is cookie data to data transmitted by $_GET<\/code><\/a> or by $_POST<\/code><\/a>.<\/li><\/ol> The problems with the actual code<\/a> are these: