Proper use of global vars in PHP - Adding to an array from a Function

Question

Context: Two functions processing xml data that needs to be combined into a single array.

I am processing from multiple feeds and combining it into a multilevel associative array, like so:

$processedData:
Array ( 
    [item1] => Array ( 
        [somedata] => tasty
        [moredata] => food
        [evenmore] => like pizza
    ) 
    [item2] => Array ( 
        [somedata] => less tasty
        [moredata] => food
        [evenmore] => like bread pudding
    )

Each function is operating on separate data, and each gives me some of the data I need; for example, somedata and moredata come from function one, while evenmore comes from function two.

function one ($xml) {
    $myPrice = new XMLReader(); //some happy XMLReader stuff that works
    $myPrice->xml($xml);
    $key = ''; 

    while ($myPrice->read()) {
        if ($myPrice->nodeType == XMLReader::ELEMENT) { //only opening tags.
            $tag = $myPrice->name;
            switch ($tag) {
                case 'TheKey':
                    $key = $myPrice->readInnerXML();
                    break;
                case 'HowGood':
                    $processedData[$key]['somedata'] = $myPrice->readInnerXML();
                    break;
                case 'TypeOfThing':
                    $processedData[$key]['moredata'] = $myPrice->readInnerXML();
                    break;
            }
        }
    }
}

Function two is structurally similar, but processes different data. Both functions should ideally return their data into one array. This can be easily accomplished by declaring global $processedData near the top of each function. Combining the return values with array_merge and + will overwrite values with the same key, according to the php manual.

Note: unlike most other questions about globals, the issue is not the input values, but the output values.

The question Are global variables in PHP considered bad practice? If so, why? suggests clearly labeling global variables to solve the common issues with global variables, but pretty much every answer on stack overflow re:Global Vars in PHP says "you can do this, but you probably shouldn't."

My Question

Is combining return values from multiple functions a good use of php globals? Is there a way to do this avoiding global variables?

Or, alternatively, what cases are a good use of php globals? When are global variables good to use?

But if have result with the same key, how could you avoid rewriting values even using global? — sectus, Oct 15 '14 at 01:00
@sectus The key is the same, but the "subkeys" are different. Using globals it works properly, as if you had done `$processedData[$key]['somedata']`, `$processedData[$key]['moredata']`, and `$processedData[$key]['evenmore']`. Your answer also works though. — Josiah, Oct 15 '14 at 01:05

score 1 · Accepted Answer · answered Oct 15 '14 at 00:58

1

You could pass your variable as second argument using reference.

function one($xml, &$processedData){}
function two($xml, &$processedData){}

It helps you to avoid using global.

http://php.net/manual/en/functions.arguments.php#functions.arguments.by-reference

answered Oct 15 '14 at 00:58

sectus

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Yes, this works. I was not familiar with the `&` pass-by-reference feature. – Josiah Oct 15 '14 at 01:02

Proper use of global vars in PHP - Adding to an array from a Function

My Question

1 Answers1