What is the significance of the warning "Cannot modify header information - headers already sent by" in PHP?

The warning "Cannot modify header information - headers already sent by" in PHP indicates that some output has already been sent to the browser before the header function is called. To solve this issue, make sure that no output is sent before using header functions, such as setting cookies or redirecting the page. 

ob_start();
// Your PHP code here

// Example of setting a cookie after output buffering
setcookie("example_cookie", "value", time() + 3600, "/");
ob_end_flush();

Keywords

PHP header information headers already sent warning significance

Related Questions