如何在控制台上打印错误？

function loginuser() {
    $results=array();
    $errors = array();

        $username = 'abc';
        $password = '123';
if ($username='') {
            array_push($errors, "Username is required");
        }
        else if ($password='') {
            array_push($errors, "Password is required");
        }


            $query = "SELECT * FROM users WHERE user_name='$username' AND user_pass='$password'";
            $result = selection($query);

        while ($row = mysqli_fetch_assoc($result)) {
        $results[] = row_jsonify($row);
    }










return json_encode($results);
return json_encode($errors);
}

Below is the code m printing but its throwing a sql error on console if i dont give a username or password i.e if i leave it empty like $username=' ';

what should i do here to print the errors on console as i dont have front end right now if the username or password is incorrect or empty

showErrsInConsole(['err1', 'error2', 'error3']);

function showErrsInConsole(array $errors)
{
    array_walk($errors, function (&$err) {
        $err = 'echo ' . $err;
    });
    $errors = implode(';', $errors);
    $exec = "gnome-terminal -x bash -c '$errors; sleep 1; read -n 1 -p \"press any key to close\"';";
    `$exec`;
}

To avoid this error "Warning: mysqli_fetch_assoc() expects parameter 1 to be mysqli_result, check if $_POST is not empty and print errors in else case just for testing.

To check if input fields are empty apply JavaScript validations to avoid empty from submission.

if(!empty($_POST["login"])) {
    $result = mysqli_query($conn,"SELECT * FROM users WHERE user_name='" . $_POST["user_name"] . "' and password = '". $_POST["password"]."'");
    $row  = mysqli_fetch_array($result);
    if(is_array($row)) {
    $_SESSION["user_id"] = $row['user_id'];
    } else {
    $message = "Invalid Username or Password!";
    }
}

Here is an example,to simplify your code, if you have any problem then try printing variables e.g. var_dump & print_r

<?php
session_start();
$conn = mysqli_connect("localhost","root","","database_ex");

$message="";
if(!empty($_POST["login"])) {
    $result = mysqli_query($conn,"SELECT * FROM users WHERE user_name='" . $_POST["user_name"] . "' and password = '". $_POST["password"]."'");
    $row  = mysqli_fetch_array($result);
    if(is_array($row)) {
    $_SESSION["user_id"] = $row['user_id'];
    } else {
    $message = "Invalid Username or Password!";
    }
}else{
  //Print error message here if no username or password provided;
  echo "Invalid credentials"; 
  print_r($_POST);
  var_dump($_POST);
}
?>