设置变量等于字符串和变量

I would like to set a variable equal to a string and a variable. The variable is a string as well coming through AJAX. I know $data3 is coming through because when I change file_put_contents('TestFile.json', $updated); to file_put_contents('TestFile.json', $data3); it works. So there's no problem with the AJAX.

I know this is not proper JSON at all, I'm just testing. The value of $data3 is the string "string". So what I want the outcome to be is "Testing string".

BELOW IS THE CURRENT CODE: <?php $data3 = $_REQUEST ["data3"]; $updated = 'Testing ' + $data3; file_put_contents('TestFile.json', $updated); ?>

You are trying to add two strings together with a JAVA style operation (+). In PHP you use . to concatenate.

$data3 = $_REQUEST['data3'];
$updated = 'Testing ' . $data3;
file_put_contents('TestFile.json', $updated);