为什么这个PHP foreach中的$ value循环一个数组？

In my jQuery code I'm creating an object like this:

var fields = [
              ['title','New Title'],
              ['description', 'New Description'],
              ['stuff', ['one','two','three']]
             ];
var objectsArray=[
                  {
                   fields:fields
                  }
                 ];

var saveObject = {
                  command: 'test',
                  callback:'testResopnse',
                  objects: objectsArray
                 }

Which I then send via ajax to a PHP page like this:

saveDataAsParseObjects(saveObject)

function saveDataAsParseObjects(saveObj){
        $.ajax({
              type: "POST",
              dataType: "json",
              url: "php/parseFunctions.php",
              data: {data:saveObj},
              success: function(response) { 
                 console.log(response);
              },
              error: function(response) {
                 console.log(response);
              }
        });
};

In my PHP page I'm doing this:

$data= $_POST['data'];

if($data['command'] == 'test'){
    testStuff($data);
}
function testStuff($data){
    $objects = $data['objects'];
    foreach($objects as $object){
        $fields = $object['fields'];
        foreach($fields as $column => $value){

            echo is_array($value) ? 'Array, ' : 'not an Array, ';
        }
    }
}

Considering my original fields array on the jQuery page, I expect testStuff() to return:

'not an Array, not an Array, Array,'.

But instead it returns:

'Array, Array, Array,'

Why is $value an array in this foreach loop when I expect it to by a string?

foreach($fields as $column => $value)

You need to loop it one more time, since your fields array is an array of arrays (take this pseudo as an example):

Array(
    INDEX => Array(...),
    INDEX => Array(...),
    INDEX => Array(...),
)

All you need is 1 more loop:

$fields = $object['fields'];
foreach($fields as $column => $value){
    foreach($value as $key => $obj) {
        echo is_array($obj) ? 'Array, ' : 'not an Array, ';
    }
}

You are iterating over this collection in most nested foreach:

var fields = [
    ['title','New Title'],
    ['description', 'New Description'],
    ['stuff', ['one','two','three']]
];

So every $value is also an array e.g. ['title','New Title']. You should iterate over it one more time or change fields to object like this:

var fields = {
    title: 'New Title',
    description: 'New Description',
    stuff: ['one','two','three']
};

because the javascript variable "fields" is an array of array.

When you loop throught $fields, you loop throught this variable (aka objectsArray[0].fields)

Because each $value is element of fields array. And each element of that array is another array.

So

['title','New Title'],

in

var fields = [
    ['title','New Title'],
    ['description', 'New Description'],
    ['stuff', ['one','two','three']]
];

is array of title and New title.

If you debug or var_dump($value) in php you will see that the output is

array (size=2)
    0 => string 'title' (length=5)
    1 => string 'New Title' (length=9)

array (size=2)
    0 => string 'description' (length=11)
    1 => string 'New Description' (length=15)

array (size=2)
  0 => string 'stuff' (length=5)
  1 => 
array (size=3)
  0 => string 'one' (length=3)
  1 => string 'two' (length=3)
  2 => string 'three' (length=5)