foreach usage

Question

Help me explain the operating principle and the meaning of $diqusql.="'{$i}'"

$diqusql="diyu IN(";

foreach($diqu as $ i){

            $diqusql.="'{$i}',";

                                    $diqusql=rtrim($diqusql, ",")." )"

Answer 1

foreach is a statement that traverses an array. The standard usage is: foreach (data type identifier in expression)

e.g:

$person = array(
"name1" => "peter",
"name2" => "lisi"
);
foreach ($person as $ person_value) {
echo "Name:" . $person_value;
echo "<br>";
}