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<?php $arr1= array('a' => "XL"); $arr2= array('a' => "XLd",'b'=>"CDW"); array_walk($arr2, function($key, &$val) use $arr1{ if(isset($arr1[$key])){ $val = $arr1[$key]; } else { $val = ''; } }); print_r($arr2);
based on 3ebQ1

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Output for Arrow functions
Parse error: syntax error, unexpected '$arr1' (T_VARIABLE), expecting '(' in /in/KC4vk on line 6

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