Strange Behaviour with Control Application

Have an issue with strange behaviour with Control Application.

The Control application works correctly on the development environment but behaves differently on the production environment.

Control application has a simple 2 x TEXTAREA fields, which perform the following task. Text from an EXCEL file is pasted into the one in the left, an AJAX button is running some PHP code to validate and once validated the output result is shown on the right-hand side field.

Works fine on the development environment, does not on the production as the PHP code is being run, content is being created but the value is not being shown in the browser.

{NonReturnedInvoices} = $content;

Content to be displayed is being concatenated in $content and then this value finally assigned to {NonReturnedInvoices} field.

Any clues?

SOLVED - Problem traced to a number_format function which worked fine on the development server but not on the production.