TypeError: Illegal invocation

Your datatype is not JSON, it’s a FormData. And for jQuery to send a FormData, it needs…
$.ajax({
    type: "POST",
    url: 'signin2.php',
    data: formData,
    processData: false, //add this
    contentType: false, //and this
})

Similar codes

17 votes293 views3 answers
Select required
Html
0 vote287 views2 answers
Html table column filter dropdown
Html
0 vote290 views1 answer
Figcaption html
Html
0 vote314 views1 answer
Webpage opaque photo caption
Html
56 votes295 views6 answers
Image in html
Html
12 votes266 views2 answers
How to web scrape with scrapy
Html
15 votes289 views2 answers
Scroll smooth css
Html
5 votes267 views6 answers
Laravel csrf token
Html
0 vote238 views1 answer
Histogram with frequency curve using seaborn
Html
1 vote278 views1 answer
Alternative image in img tag
Html