mysql - Need explanation of this php code $variable = array(); -

excuse me possibly stupid question, need understand how code works. searched google , no understandable answer

here code:

$data = array_merge($one,$two); $sql = "insert msql_table (one, two) values "; $insertquery = array(); $insertdata = array(); foreach ($_post['one'] $i => $one) {     $insertquery[] = '(?, ?)';     $insertdata[] = $one;     $insertdata[] = $_post['two'][$i]; } if (!empty($insertquery)) {     $sql .= implode(', ', $insertquery);     $stmt = $db->prepare($sql);     $stmt->execute($insertdata); } 

can not understand code:

$insertquery = array(); $insertdata = array(); 

usual code "insert msql_table (one, two) values (?, ?)";

i understand values $insertquery = array(); , array() defined latter.... big mess in head.

may link information code (explanation of code)? want understand these 2 lines do

those 2 lines initialize variable, , creates empty array. way, when data inserted array later, php won't complain (depending on error_reporting) variable doesn't exist.

here's link http://php.net/manual/en/language.variables.basics.php