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up vote 47 down vote favorite
11

I was wondering if it is possible to edit the current object that's being handled within a foreach loop

I'm working with an array of objects $questions and I want to go through and look for the answers associated with that question object in my db. So for each question go fetch the answer objects and update the current $question inside my foreach loop so I can output/process elsewhere.

foreach($questions as $question){
    $question['answers'] = $answers_model->get_answers_by_question_id($question['question_id']);
}
share|improve this question
    
how about references? – Artjom Kurapov Apr 12 '12 at 10:08
    
As both ArtjomKurapov and @topener suggested I was looking for 'pass by reference' using the & sign. Thanks chaps :) have a nice day – Garbit Apr 12 '12 at 10:12
    
@Garbit awesome. Could you please mark my answer as best if it helped you? – Rene Pot Apr 12 '12 at 12:05
up vote 84 down vote accepted

There are 2 ways of doing this

   foreach($questions as $key => $question){
        $questions[$key]['answers'] = $answers_model->get_answers_by_question_id($question['question_id']);
    }

This way you save the key, so you can update it again in the main $questions variable

or

foreach($questions as &$question){

Adding the & will keep the $questions updated. But I would say the first one is recommended even though this is shorter (see comment by Paystey)

Per the PHP foreach documentation:

In order to be able to directly modify array elements within the loop precede $value with &. In that case the value will be assigned by reference.

share|improve this answer
    
Nice! so the & sign will pass by reference? is that the correct terminology? – Garbit Apr 12 '12 at 10:09
    
you are missing part with passing entire $question variable into get_answers_by_question_id() – Artjom Kurapov Apr 12 '12 at 10:10
    
Correct. I just added a link to the docs about that – Rene Pot Apr 12 '12 at 10:11
17  
References in foreach is really not recommended, the way the foreach passes around the value part of the loop results in unpredicatble behaviour. It may be longer but you're far safer using method 1 here. – Paystey Apr 12 '12 at 10:11
2  
@Paystey can you cite your sources or give a detailed explaination ? – Nico Oct 8 '15 at 14:22

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