The return value of a recursive method in PHP

{Code ...} this method is used to obtain the corresponding val value for the Mark $ key. I return $ v at the end of the method, and then I assign the return result to a value $ va, this value is always blank, but I have a value when printing $ v at the end of the method. why? Is variable...

  Array ('1a '=> '', '3a' =>'', '6a '=> array ('6a1' => '', '6a2 '=> '', '6a3' => array ('6a31 '=>'', '6a33' => '', '6a34' => '1',), 1 => array ('3B '=> '', '4b '=> array ('4b1' => '', '4b2 '=>'',), '6b' => '',)); function search_val ($ key, $ arr) {$ v = ''; foreach ($ arr as $ ks =>$ vs) {if ($ ks! = $ Key & is_array ($ vs) {search_val ($ key, $ vs);} else if ($ ks! = $ Key & is_string ($ vs) {continue;} else if ($ ks ==$ key) {$ v =$ vs; break ;}} return $ v; // var_dump ($ v); exit; // here there is a value of 1 // echo $ v; // Test to directly output} $ va = search_val ('6a34', $ array); var_dump ($ va); // $ va is always empty

This method is to mark$keyRetrieve the correspondingvalAt the end of the method.return $vAnd then IreturnThe result is assigned to a value.$vaThis value is always null, but I have a value when printing $ v at the end of the method. why? Is it caused by the scope of variables or by nonstandard code writing? Solution

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  Array ('1a '=> '', '3a' =>'', '6a '=> array ('6a1' => '', '6a2 '=> '', '6a3' => array ('6a31 '=>'', '6a33' => '', '6a34' => '1',), 1 => array ('3B '=> '', '4b '=> array ('4b1' => '', '4b2 '=>'',), '6b' => '',)); function search_val ($ key, $ arr) {$ v = ''; foreach ($ arr as $ ks =>$ vs) {if ($ ks! = $ Key & is_array ($ vs) {search_val ($ key, $ vs);} else if ($ ks! = $ Key & is_string ($ vs) {continue;} else if ($ ks ==$ key) {$ v =$ vs; break ;}} return $ v; // var_dump ($ v); exit; // here there is a value of 1 // echo $ v; // Test to directly output} $ va = search_val ('6a34', $ array); var_dump ($ va); // $ va is always empty

This method is to mark$keyRetrieve the correspondingvalAt the end of the method.return $vAnd then IreturnThe result is assigned to a value.$vaThis value is always null, but I have a value when printing $ v at the end of the method. why? Is it caused by the scope of variables or by nonstandard code writing? Solution

The function is changed to the following. your logic is a bit problematic. return is used for data interaction between methods. The final value obtained can be search_val, which is returned for you. Therefore, return is directly returned here.

 function search_val($key, $arr) {            foreach ($arr as $ks => $vs) {                if($ks != $key && is_array($vs)) {                    return search_val($key, $vs);                }else if($ks != $key && is_string($vs)) {                    continue;                }else if($ks == $key) {                    return $vs;                }            }            //return $v;            //var_dump($v);        }        

To put it bluntly, recursion means calling itself.
In your code, function calls do not obtain their return values.
Pay attention to the processing of the returned results.

function search_val($key, $arr) {    if (!is_array($arr) || empty($arr)) {        return false;    } else {        foreach ($arr as $k => $v) {            if ($k === $key) {                return $v;            }             if (is_array($v) && !empty($v)) {                $re =  search_val($key, $v);                if ($re !== false) {                    return $re;                }             }             continue;        }    }    return false;}