PHP foreach Report "Cannot create references to elements of ..." Workaround

Today in the project with the PHP foreach database query results, in order to facilitate not to determine whether the data exist, directly with (array) to force the conversion of data, just start Web page always open, reported 502, a Meng, suddenly php newspaper "cannot create references To elements of a temporary array expression ", find the error line, the original code is as follows:

foreach ((array) $net _arr as $k = = & $val) {        $network [$val [' Node_ip ']][$val [' ifname '] = $val;}

Later changed to the following code, everything back to normal.

if (!empty ($net _arr)) {        foreach ($net _arr as $k = = & $val) {            $network [$val [' Node_ip ']][$val [' ifname ']] = $ val;    }}