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up vote 0 down vote favorite

Looking to get a count of particular key=>values in an multi dimensional array. What I have works i.e. the result is correct, but I can't seem to get rid of the Undefined Index notice. 

$total_arr = array();

foreach($data['user'] as $ar) {
     $total_arr[$ar['city']]++;
}

print_r($total_arr);

Any ideas? I have tried isset within the foreach loop, but no joy...

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Possibly related: PHP isset() function misbehaving –  Amal Murali Oct 24 '13 at 14:13

2 Answers 2

up vote 2 down vote accepted 
$total_arr = array();

foreach($data['user'] as $ar) {
    if(array_key_exists($ar['city'],$total_arr) {
        $total_arr[$ar['city']]++;
    } else {
        $total_arr[$ar['city']] = 1; // Or 0 if you would like to start from 0
    }
}    

print_r($total_arr);
share|improve this answer
    
Correct answer. And if one wanted this a little bit “shorter”, one could also mis-use the ternary operator slightly, and replace the whole if/else construct with simply isset($total_arr[$ar['city']) ? $total_arr[$ar['city']++ : $total_arr[$ar['city'] = 1; –  CBroe Oct 24 '13 at 14:15
    
isset is usually always faster than array_key_exists and you'll never have to bother about NULL values here, so go with isset instead. –  h2ooooooo Oct 24 '13 at 14:15
    
Strangely enough, replacing 'array_key_exists' with 'isset' produces the same undefined index error. Thanks for the solution ogres! –  Solaris76 Oct 24 '13 at 14:23
up vote 1 down vote

PHP will throw that notice if your index hasn't been initialized before being manipulated. Either use the @ symbol to suppress the notice or use isset() in conjunction with a block that will initialize the index value for you.

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