How to Show Columns in a table - php

Question

I'm learning PHP and am trying to create some code outside of the tutorial I've been watching to understand it better and I can't seem to figure out where I'm going wrong with the code below. I have lots of other functions working just fine, just not this one. Can anyone point me in the right direction? Thanks.
The result I get is Catchable fatal error: Object of class User could not be converted to string on line 20, which is echo $user . "<br /><br />";
Here is my index.php
<?
$users = User::db_fields();
foreach($users as $user) {
echo $user . "<br /><br />";
}
?>
Here is my class User in user.php
<?php
class User extends OtherStuff {
public static function db_fields() {
global $db;
return static::find_by_sql("SHOW COLUMNS FROM my_table");
}
}
<?
Here is some of my OtherStuff class in other_stuff.php
class OtherStuff {
public static function find_by_sql($sql="") {
global $db;
$result_set = $db->query($sql);
$object_array = array();
while($row = $db->fetch_array($result_set)) {
$object_array[] = static::instantiate($row);
}
return $object_array;
}
public static function instantiate($record) {
$class_name = get_called_class();
$object = new $class_name;
foreach($record as $attribute => $value){
if($object->has_attribute($attribute)) {
$object->$attribute = $value;
}
}
return $object;
}
}
?>

Answer 1

Well....Your calling db_fileds() statically.
User::db_fields();
So it needs to be a static function..
public static function db_fields() {
EDIT
You could do this as a workaround...
Change your query
return static::find_by_sql("SELECT * FROM mytable LIMIT 1");
Then do this...
$fields = User::db_fields();
foreach($fields as $key=>$value ) {
echo $key; // This will give the field name
}
EDIT 2
To preserve the column names linked to the fields.
Although this is likely wrong, because now its instantiating multiple times, and what happens in a case where an object doesnt find an attribute and doesn't get written, then you miss a column.
But the idea is there...
while($row = $db->fetch_array($result_set)) {
foreach($row as $k=>$v){
$object_array[$k] = static::instantiate($row);
}
}

Answer 2

Well the array you're iterating over is $users, and the values you're getting from $users are going into $user.
But you're echoing $users (the Array). If the values in your $users array are all strings (or some other scalar value) you should be fine by changing your code to:
<?
$users = User::db_fields();
foreach($users as $user) {
echo $user . "<br /><br />";
}
?>
(I also added in your missing brace at the end)

Answer 3

You made a silly:
echo $users . "<br /><br />"; should have $user as the echo param
<?
$users = User::db_fields();
foreach($users as $user) {
echo $user . "<br /><br />";
?>
You were printing the original array every time
Edit:
The new error is a reflection of the fact that your User class does not explicitly define a way for objects of the class to be converted to strings. If you want to do a quick n dirty output, you can var_dump() your objects, but eventually you'll want to override the __toString() method. Check this out.
You can also simply make a function in the User class that returns the string you want and just call it with $user->StringifyUser(). The (main) difference between this approach is that PHP will not implicitly convert your User class objects to strings when used in your originally context.
Edit 2:
I would also check out the other answers, especially that of KyleK who addresses several key points that I did not touch on.