What are some common reasons for the "headers already sent" error in PHP?

The "headers already sent" error in PHP occurs when the server tries to send HTTP headers, but output has already been sent to the browser. This can be caused by whitespace or text before the opening <?php tag, using functions like echo or print before sending headers, or including files with whitespace after closing ?> tags. To solve this issue, ensure that no output is sent before sending headers and avoid using functions that send output before sending headers. 

&lt;?php
ob_start(); // Start output buffering
// Your PHP code here
ob_end_flush(); // Flush output buffer

Keywords

output buffering whitespace include files UTF-8 encoding session_start

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