Seperate treatment of last/first entry in loop (that has a subloop) - php

Question

I have some troubles with the following situation. I want to output nested information that looks a bit like this:
"name": "X",
"children": [
{
"name": "categories",
"children": [
{
"name": "Cat A",
"children": [
{"name": "B"},
{"name": "C"},
{"name": "D"}
]
},
{
"name": "Cat B",
"children": [
{"name": "C"},
{"name": "D"}
]
}
In this case you see that the last } of child Cat A has an comma at the end, while the last nest (Cat B) does not have comma at the end. In a previous topic I learned how to resolve the comma within the the inner loop ({"name": "D"}). However, using the implode (with sprintf instead of printf) at the end of the first while loop (see code below) created double prints of the data.
This is what the code looks like (slightly adjusted):
while ($ucs = mysqli_fetch_object($uc))
{
printf('{');
printf('"name": "%s",', $ucs->cat);
/*for ($i = 0; $i < 100; $i++)
{
$cat_name = $ucs->cat;
}*/
printf('"children": [');
$rtitle = "SELECT title FROM table WHERE genre='$category'";
//Some other code of lesser relevance for this issue
$names = array();
while ($title2 = mysqli_fetch_object($ptitles)) {
$names[] = sprintf('"name": "%s"', $title2->title);
}
echo implode(',', $names);
printf(']');
printf('},');
//Some other code
Now the main issue is to have the comma out of the last print statement.
However, using implode for the category did not work out. In the previous topic a user pointed me out to add it before the code if it isn't the first output. However, would that work in this scenario? If so, how could I flag whether this is the first iteration?
I hope someone can help me out here,
Help is again very much appreciated,
Thanks in advance!

Answer 1

At the beginning of your loop set a variable to 0 and at the end of the loop increment it by 1. Then, use an if statement to see if the variable is equal to 0.
Use json_encode(), though. It will lead to cleaner, more maintainable code.