PHP Array strange behavior - php

Question

I am using a PHP Class that is generating a nested categories tree menu in json format from a MySQL database. The problem is that the array used to fill the data doesn't do what it is supposed to
The PHP Class is:
class nestedCategories {
public $json = array();
public function generateMenu($categories,$level){
$this->json = array();
foreach($categories as $category ){
$this->json['title'] = $category->description;
$this->json['expanded'] = true;
if(isset($category->children) && count($category->children)>0){
$this->json['folder'] = true;
$this->json['children'] = $this->generateMenu($category->children,$category->category_id);
} else {
$this->json['folder'] = false;
}
}
}
public function getJSON() {
return $this->json;
}
The $json is supposed to look like:
[
{"title": "Animalia", "expanded": true, "folder": true, "children": [
{"title": "Chordate", "folder": true, "children": [
{"title": "Mammal", "children": [
{"title": "Primate", "children": [
{"title": "Primate", "children": [
]},
{"title": "Carnivora", "children": [
]}
]},
{"title": "Carnivora", "children": [
{"title": "Felidae", "lazy": true}
]}
]}
]},
{"title": "Arthropoda", "expanded": true, "folder": true, "children": [
{"title": "Insect", "children": [
{"title": "Diptera", "lazy": true}
]}
]}
]}
]
but, when I am trying to pull the data from MySQL, the $json array only gives me the last pulled data from MySQL, as if it is erasing all data behind
Could someone talk me trough?

Answer 1

You are overwriting the array with each loop around categories, and wiping out the member variable with an array assignment each time round.
Plus, I suspect that it won't return the structure you're looking for unless you make it preoperly recursive (which means returning the array that you've built):
class nestedCategories {
public function generateMenu($categories,$level){
$categoriesJson = array();
foreach($categories as $category ){
$categoryJson = array();
$categoryJson['title'] = $category->description;
$categoryJson['expanded'] = true;
if(isset($category->children) && count($category->children)>0){
$categoryJson['folder'] = true;
$categoryJson['children'] = $this->generateMenu($category->children,$category->category_id);
} else {
$categoryJson['folder'] = false;
}
$categoriesJson[] = $categoryJson;
}
return $categoriesJson;
}
}
You would now just get back the data by calling generateMenu rather than using the member variable.

Answer 2

You are setting $this->json = array(); at the top of your generateMenu method. When you make the recursive call it destroys what was written to the array on the previous call.
In addition in each recursive call $this->json['title'] will over write the previous title. The same goes for expanded, children and folder.
It looks like I took a little longer that I should have to make the example code. Here it is anyway.
class Foo {
public function generateMenu($categories){
$json_array = array();
foreach($categories as $category) {
$json_object = array();
$json_object['title'] = $category->description;
if(isset($category->children) && count($category->children)>0){
// it looks like expanded should only be
// in objects with > 0 children
$json_object['expanded'] = true;
$json_object['folder'] = true;
$json_object['children'] = $this->generateMenu($category->children);
} else {
// based on the json in the question it looks like
// it should always contain a children array, but no folder element
$json_object['children'] = array();
}
$json_array[] = $json_object;
}
return $json_array;
}
}
Here is the test data:
$Diptera = new stdClass();
$Diptera->description = 'Diptera';
$Insect = new stdClass();
$Insect->description = 'Insect';
$Insect->children = array($Diptera);
$Arthropoda = new stdClass();
$Arthropoda->description = 'Arthropoda';
$Arthropoda->children = array($Insect);
$Felidae = new stdClass();
$Felidae->description = 'Felidae';
$Carnivora2 = new stdClass();
$Carnivora2->description = 'Carnivora';
$Carnivora2->children = array($Felidae);
$Carnivora = new stdClass();
$Carnivora->description = 'Carnivora';
$Primate2 = new stdClass();
$Primate2->description = 'Primate';
$Primate = new stdClass();
$Primate->description = 'Primate';
$Primate->children = array($Primate2, $Carnivora);
$Mammal = new stdClass();
$Mammal->description = 'Mammal';
$Mammal->children = array($Primate, $Carnivora2);
$Chordate = new stdClass();
$Chordate->description = 'Chordate';
$Chordate->children = array($Mammal);
$Animalia = new stdClass();
$Animalia->description = 'Animalia';
$Animalia->children = array($Chordate);
$catagories = array($Animalia);
Here is how it's called:
$f = new Foo();
echo json_encode($f->generateMenu($catagories), JSON_PRETTY_PRINT);
Here is the output:
[
{"title": "Animalia", "expanded": true, "folder": true, "children":
[
{"title": "Chordate", "expanded": true, "folder": true, "children":
[
{"title": "Mammal", "expanded": true, "folder": true, "children":
[
{"title": "Primate", "expanded": true, "folder": true, "children":
[
{"title": "Primate", "children": []},
{"title": "Carnivora", "children": []}
]
},
{"title": "Carnivora", "expanded": true, "folder": true, "children":
[
{"title": "Felidae", "children": []}
]
}
]
}
]
},
{"title": "Arthropoda", "expanded": true, "folder": true, "children":
[
{"title": "Insect", "expanded": true, "folder": true, "children":
[
{"title": "Diptera", "children": []}
]
}
]
}
]
}
]

Answer 3

You are overwriting the array keys when you iterate over the JSON.
$array = array();
$array['foo'] = 'bar';
//$array['foo] = 'bar';
$array['foo'] = 'foo';
//$array['foo'] = 'foo';