Only variables should be passed by reference

Question

I have a class:

class Validator {
    private $validationArray;
    private $cleanedValues;

    public function __construct($arg1, $arg2=NULL) {
        if(empty($arg2)) {
            $this->LoadValidatorByName($arg1);
        } else {
            $this->LoadValidatorFromLeadType($arg1, $arg2);
        }
    }

    private function LoadValidatorFromLeadType($lead_type, $vocabulary) {
            $ErrorReporter = new ErrorReporter;
            $taxonomy_term = reset(taxonomy_get_term_by_name($lead_type, $vocabulary));

...some more stuff

The function taxonomy_get_term_by_name is a Drupal function but the issue I am experiencing is a PHP one.

When this method is called PHP complains with:

Strict warning: Only variables should be passed by reference in Validator->LoadValidatorFromLeadType() (line 32 of [path to my file])

Line 32 is ths line with:

$taxonomy_term = reset(taxonomy_get_term_by_name($lead_type, $vocabulary));

I've looked in to the error and I'm pretty sure I know what it means, but I can't understand what is wrong with my code that causes this warning.

score 21 · Accepted Answer · answered Dec 04 '12 at 08:47

21

reset is waiting for a variable reference. You are passing it a function result...

$taxonomy_term = taxonomy_get_term_by_name($lead_type, $vocabulary);
$taxonomy_term = reset($taxonomy_term );

answered Dec 04 '12 at 08:47

Salketer

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score 10 · Answer 2 · answered Dec 04 '12 at 08:46

10

This mean that only variable should be passed by reference, not an expression.

reset($array_variable); // correct

and

reset(some_function_that_returns_array()); // incorrect

If you take a second and think about it more - you would find that reset() with expression (not a variable) makes no sense, because you've rewind the array pointer to the beginning, but you don't have the ability to access that array anymore.

answered Dec 04 '12 at 08:46

zerkms

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That's why PHP offers array access on function results since PHP 5.4: `taxonomy_get_term_by_name($lead_type, $vocabulary)[0]` – Sven Dec 04 '12 at 08:52
@Sven: if only you knew the first element's key – zerkms Dec 04 '12 at 08:53

score 2 · Answer 3 · answered Dec 04 '12 at 08:48

2

You should only reset a variable (which is passed by reference), not a return value of a function. see: http://www.php.net/reset

answered Dec 04 '12 at 08:48

Tobias

1,692
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Only variables should be passed by reference

3 Answers3

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