appending array to FormData and send via AJAX

You can also send an array via FormData this way:

var formData = new FormData;var arr = ['this', 'is', 'an', 'array'];for (var i = 0; i < arr.length; i++) {    formData.append('arr[]', arr[i]);}

So you can write arr[] the same way as you do it with a simple HTML form. In case of PHP it should work.

You may find this article useful: How to pass an array within a query string?

You have several options:

Convert it to a JSON string, then parse it in PHP (recommended)

JS

var json_arr = JSON.stringify(arr);

PHP

$arr = json_decode($_POST['arr']);

Or use @Curios's method

Sending an array via FormData.

Not recommended: Serialize the data with, then deserialize in PHP

JS

// Use <#> or any other delimiter you wantvar serial_arr = arr.join("<#>"); 

PHP

$arr = explode("<#>", $_POST['arr']);

Typescript version:

export class Utility {          public static convertModelToFormData(model: any, form: FormData = null, namespace = ''): FormData {        let formData = form || new FormData();        let formKey;        for (let propertyName in model) {            if (!model.hasOwnProperty(propertyName) || !model[propertyName]) continue;            let formKey = namespace ? `${namespace}[${propertyName}]` : propertyName;            if (model[propertyName] instanceof Date)                formData.append(formKey, model[propertyName].toISOString());            else if (model[propertyName] instanceof Array) {                model[propertyName].forEach((element, index) => {                    const tempFormKey = `${formKey}[${index}]`;                    this.convertModelToFormData(element, formData, tempFormKey);                });            }            else if (typeof model[propertyName] === 'object' && !(model[propertyName] instanceof File))                this.convertModelToFormData(model[propertyName], formData, formKey);            else                formData.append(formKey, model[propertyName].toString());        }        return formData;    }}

Using:

let formData = Utility.convertModelToFormData(model);