I have a function that retrieves some data from the database, formats it as HTML and then stores this HTML into a variable, $output. The problem is that $output cannot be echoed on the screen now, only later, after other functions run. Also this data must be retrieved at this stage, not later.
So how can I call this $output variable in another function, after output to the screen has started?
You could define $output in the main script, and import it into a function:
function output()
{
global $output;
This will probably work for your situation at hand. However, it is considered bad practice to use the global variable space with stuff like this, and rightly so. (Believe me, I've done it for years. :)
There are some other approaches that are better for long-term code quality and maintainability.
Global config array
You could either keep one global array for all global settings. Do this somewhere in your main script:
$config = array();
$config["output"] = "<html>.......</htmL>";
$config["user_language"] = "en";
.....
you import the configuration array into the function like so:
function output()
{ global $config;
echo $config["output"];
Registry pattern
if you want to do some reading, you could use something more advanced like the Registry Pattern. The snippet shown here looks a nice example for a registry. The Zend Framework also has a class for this.
But things like a Registry are really, really advanced, and probably not necessary for you at this point. I would suggest using one central config array. Should the need for something more complex arise, the config array is easy to find and replace.
Context: Are global variables in PHP considered bad practice?
welcome to using returns, and passing parameters:
DO NOT USE global , it breaks encapsulation, one of the cornerstones of object oriented programming, and can lead to incredibly hard to maintain code.
<?php
function doSomethingInDb(){
$value = db_result(); //something from the database, this is psuedo code
return $value
}
function displaySomethingFromDb($input){
echo($input); //or some other way of displaying
}
//calulate results
$output = doSomethinginDb();
//do other stuff...
//output the result when you need it...
displaySomethingFromDb($output);
You have to pass the variable via a function argument, or define it as global inside the function.
$output = '<p>macilaci</p>';
function doesathing($output)
{
echo $output;
}
OR
function doesathing()
{
global $output;
echo $output;
}
don't put the data in a variable inside the function which retrieves it.
function retrieve(...)
{
... fetch from db
return $rv;
}
function other() {...}
function still($data)
{
...
echo $data;
}
$output = retrieve(...);
other();
still($output);
Rather than just putting this snippet into a global variable, IMHO a better solution is to use a templating system to construct the elements of the page.
NB I'm not suggesting you immediately rush out and start downloading Smarty - although there are benefits and drawbacks to completely seperating logic and presentation, there are only benefits in taking a modular approach to your screen layout.
C.
Put the following line at the start of the function that defines $output:
global $output;
Put the same line at the start of any function that will make use of it.
(This will not work, or will interfere with other variables, if there is already a variable called $output in the global scope.)
Use Session
For example:
session_start();
$query = '...........';
$result = mysql_query($query);
$_SESSION['mysqlResult'] = $result;
Now you can use it from any page at any time by simply calling like this
$myresult = $_SESSION['mysqlResult'];
