Looping with Object Operators - php

Question

I am playing around with PHP Calendar (Corey Worrell) and had a question regarding instance looping. In order to initialize the calendar, I have to output this:
$calendar->standard('today')
->standard('prev-next')
->standard('holidays')
->attach($event1)
->attach($event2)
->attach($event3)
->attach($event4)
->attach($event5)
->attach($event6)
->attach($event7)
->attach($event8)
->attach($event9)
->attach($event10)
->attach($event11)
->attach($event12)
->attach($event13)
->attach($event14)
->attach($event15)
->attach($event16)
->attach($event17);
Each ->attach($event#) outputs an event on the calendar. I want to loop through these numerically incrementing event names but adding a for loop anywhere in that code breaks everything, outputting this error:
PHP Catchable fatal error: Argument 1 passed to
Event_Subject::attach() must be an instance of Event_Observer, null
given, called in /calendar/index.php on line 75 and defined in
/calendar/classes/event_subject.php on line 21
Here is the loop I've tried:
$calendar->standard('today')
->standard('prev-next')
->standard('holidays')
for ($inc = 0; $inc <= $number_of_events; $inc++) {
if ($inc == $number_of_events) {
->attach($$event_name);
}
else {
->attach($$event_name)
}
}
How can I loop inside of here? My events are stored in MySQL and I am doing an $number_of_events = $result->num_rows to determine the number of events returned. The ->attach($event#) would loop, repeating until the total $number_of_events is hit.

Answer 1

That's called method chaining. Each method of the class returns an instance of the called object via $this, allowing you to stack method calls. Method chaining is possible because the function returns a reference to your object.
Because each function in the class that supports method chaining returns the calling object, you can just re-assign the returned object back into the original $calander variable;
for ($inc = 0; $inc <= $number_of_events; $inc++) {
if ($inc == $number_of_events) {
$calander = $calander->attach($event1);
}
else {
$calander = $calander->attach($event1);
}
}
Additionally, if you wanted to iterate through variable names, you could use a variable variable inside your loop;
$variable = "event".$inc;
$calander = $calander->attach($$variable);
So this would become $event0, $event1, $event2, etc.

Answer 2

The problem with the loop is that there is nothing in front of the -> operator. The -> references a property of an object, but you do not provide it with an object. You could solve it by putting $calendar in front of the lonesome operators ($calendar->...), but it would still not be very pretty code.
I suggest this instead:
I think you could just add the events one by one inside the loop I assume you are already using to create the $event1, $event2, etc. I don't know what you are using to get the data out of the database or what your table structure looks like, but I will provide an example for MySQLi. It should be easy to modify for other alternatives.
//Add the standards.
$calendar->standard('today')
->standard('prev-next')
->standard('holidays');
//Connect to the database here and query for the events using MySQLi.
//Loop through the results.
while($row = $result->fetch_assoc()) {
//Create an event from the database row...
$event = calendar->event()
->condition('timestamp', $row['TIMESTAMP'])
->title('Hello All', $row['TITLE'])
->output('My Custom Event', $row['OUTPUT']);
//...and attach it.
$calendar->attach($event);
}
This is not code to be copy-pasted directly, but more of a suggestion about how to organize it.
Also, for the future, you should not name variables $name1, $name2, etc and then use $$ to reference them. Use arrays instead.

Answer 3

Here's the solution. Not sure why changing this to reference $calendar each line worked, but it did. Thanks everyone.
$calendar->standard('today');
$calendar->standard('prev-next');
$calendar->standard('holidays');
for ($x = 1; $x <= $number_of_events; $x++) {
$event_name = "event".$x;
$calendar->attach($$event_name);
}