$values = [ 'a'=>null, 'b'=>'abc', ]; foreach($values as $key => &$value) { // 単純にコードがおかしいのだが、二週目にエラーなので気付かず $value[$key] = strtoupper($value); // ホントはこう書きたかったのだ // $value = strtoupper($value); } $ng = 1; $ng['abc'] = 2; // PHP Warning: Cannot use a scalar value as an array $ok = null; $ok['abc'] = 2; // => ['abc'=>'2']
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