Undefined property within foreach unless print_r'd - php

Question

I feel I must be missing something here. PHP displays: "Notice: Undefined property: DateTime::$date" when trying to display a property from an outer loop but if I print_r() the line before, then it prints the value with no error. Comment it out again, and the error comes back?
I suspect perhaps $iteration['EventTime']->date is getting confused with the date() function in PHP but am not sure how to overcome this via an escape. I cannot change the format of the object.
Object:
array (size=6)
'LINE' => string '2' (length=1)
'EventTime' =>
object(DateTime)[2]
public 'date' => string '2019-09-11 01:25:10.000000' (length=26)
public 'timezone_type' => int 3
public 'timezone' => string 'Europe/London' (length=13)
'Tag' => string 'PLC32.J.A.10.NOREAD' (length=19)
'Area' => string 'Material\PLC32' (length=14)
'Message' => string '32JA10 Consecutive No-read Fault' (length=32)
'FAULT_STATE' => int 1
Loop:
foreach ($sqlsrv_fetch_all as $index => $row) {
if ($row['FAULT_STATE'] == 1) {
foreach ($sqlsrv_fetch_all as $iteration) {
if ($iteration['LINE'] < $row['LINE'] || $iteration['Tag'] != $row['Tag'] || $iteration['FAULT_STATE'] == 1) {
continue;
} else {
//print_r($row);
echo "row: ".$row['EventTime']->date;
}
}
}
}
Should output "row: 2019-09-11 01:25:10.000000";
But unless I call print_r() first, it errors and outputs nothing.

Answer 1

This is actually a bug in PHP (I'm yet to find its ID in the bugtracker) that has been fixed with PHP 7.4 - see here.
print_r is one of a few ways to display internals of an object, including its private properties. Apparently, before PHP 7.4, calling print_r on an object caused its properties to become public (presumably using reflections, so that their contents could be displayed), but never turned back after that.
The documentation does not name \DateTime::$date as a public field. If you want to display date, use \DateTime::format() method instead.