PHP简单的功能不起作用

Question

I can't make a simple echo.

I have an admin.class.php

public static function get_quota() {
  return self::find_by_sql("SELECT * FROM quota");
}

public static function find_by_sql($sql="") { 
  global $database; 
  $result_set = $database->query($sql); 
  $object_array = array(); 
  while ($row = $database->fetch_array($result_set)) { 
    $object_array[] = self::instantiate($row); 
  } 
  return $object_array; 
}

And my echo code in index.php

<?php
    $admin = User::find_by_id($_SESSION['user_id']);
    $admin_class = new Admin();
    $get_quota = Admin::get_quota();
    $sql = "SELECT * FROM quota";
    $get_quota = Admin::find_by_sql($sql);
?>
.
.
.
<?php echo $get_quota->daily_a; ?>

So my problem is, that the code is not working. I cannot echo my data. Can you help me, please?

Answer 1

You have a couple of problems here:

<?php echo $get_quota->daily_a; ?>

This line references the $get_quota variable and searches for a member field daily_a. Try this:

<?php echo "Quota is:".var_export($get_quota->daily_a,true); ?>

This will show that that is simply an empty variable.

However, also note:

$get_quota = Admin::get_quota();
$sql = "SELECT * FROM quota";
$get_quota = Admin::find_by_sql($sql);

Here you are calling two separate methods from Admin and setting the variable $get_quota to the result. The second overwrites the first. Therefore the get_quota() method doesn't help us here: we need to know what your find_by_sql() method returns.

EDIT (Post new code added to question)

You can implement logging/echoing within the function you've a problem with:

public static function find_by_sql($sql="") { 
  global $database; //Note this is bad practice (1).
  $result_set = $database->query($sql); 
  echo "Result Set: ".var_export($result_set,true)."
";//This should return something if you're getting something back from the database. Also, remove this for runtime (obviously).

  if (count($result_set) <= 0) { //constraint checking is always good! And cheap!
    error_log("An unexpected number of rows (0) was received from the database for query='".$sql."'.");
  }

  $object_array = array(); 
  while ($row = $database->fetch_array($result_set)) { 
    $object_array[] = self::instantiate($row); //Ensure that the instantiate function returns something!
  } 

  echo "Object Array: ".var_export($object_array, true)."
";//double-check your instantiate function is working
  return $object_array; 
}

Based on this code, your problem is likely with the instantiate function; if it's not returning anything, $object_array is probably empty. (But not null!).

(1) You should avoid grabbing global variables like this. Instead, instantiate a class that holds and manages your database connection. Then make your find_by_sql function non-static and have a member field pointing to your database.