Php文件输出变量

Okay I'm working with this code

$Output = $FirstName '_' $LastName '_' $AccountNumber;
file_put_contents($Output, 'ENTER HTML');

How can I make it output the file by the variable determined ? For some reason it just returns an error.

You forgot to concatenate your 3 variables:

$Output = $FirstName . '_' . $LastName . '_' . $AccountNumber;

$Output = $FirstName .'_'. $LastName .'_'. $AccountNumber; // missing concatenate operator
file_put_contents($Output, 'ENTER HTML'); 

For help on file_put_contents visit http://php.net/manual/en/function.file-put-contents.php