PHP - Get object properties by variable - php

Question

I have an object with lots of properties. Some of the properties have their names start with the same string of text (in my example to come "bullet"), followed by an integer.
I can fetch the property values as follows:
echo $objectName->bullet1;
echo $objectName->bullet2;
echo $objectName->bullet3;
and so on.
I'm trying to write a for loop to get the first 20 of these, and at the moment it looks a bit like:
for ($i = 1; $i <= 20; $i++){
if ($objectName->bullet$i){
echo $objectName->bullet$i;
}
}
But this isn't working. I know I could write something like
$bulletsArray[1] = $objectName->bullet1;
$bulletsArray[2] = $objectName->bullet2;
$bulletsArray[3] = $objectName->bullet3;
all the way through to 20, then put a for loop on that, but I'm sure there must be a cleaner way. Can someone point me in the right direction?

Answer 1

This is how you can do it:
for ($i = 1; $i <= 20; $i++){
$propertyName = "bullet$i";
if ($objectName->$propertyName){
echo $info->$propertyName;
}
}
Though I think using an array instead of the object would be a better solution.

Answer 2

$var = 'myVariable';
$value = $object->$var;
is the correct syntax for accessing a field by name in PHP.
In your case it would look something like this:
for ($i = 1; $i <= 20; $i++)
{
$var = 'bullet'.$i;
if ($objectName->$var)
{
echo $info->$var;
}
}

Answer 3

Both previous answers have the "try it, if it doesn't work, move on" and are working for a very specific situation. Let me give you a more generic approach, which, sadly, requires PHP 5.
A bit about Reflection
Reflection allows you to reflect on an object or class to extract useful information about it. In particular, you can use Reflection to get all the properties set in a class, whether static, at run-time, or generated on the go.
To do this, start by initiating your Reflection object (assuming your class object is $object) as follows:
$refObj = new ReflectionObject($object);
This will now give you a reflection interface. Notice the useful ReflectionObject::getProperties() method - it allows you to get all properties set in a class (and you can filter by public, protected, private etc... if needed). We'll use exactly this:
$yourNewArray = array();
$PropertyArray = $refObj->getProperties();
$pCount = count($PropertyArray);
for ($i = 0; $i < $pCount; $i++) {
$yourNewArray[$PropertyArray[$i]->getName()] = $PropertyArray[$i]->getValue($object);
}
Done. Completely generic, works anywhere.

Answer 4

in my system, which doesn't allow me to do
$myPropertyValue = $object->$property;
I still can get to the value of the 'variable' property name with the function below; you can set $property without php complaining about syntax or throwing errors.
<?php
class MyClass{
public function getProperty($propertyName){
$props=get_object_vars($this);
if (array_key_exists($propertyName,$props)){
return $props[$propertyName];
}else{
return FALSE;
}
}
}
?>