How can including unnecessary spaces or characters in PHP code lead to the "headers already sent" error?

Including unnecessary spaces or characters in PHP code can lead to the "headers already sent" error because these extra characters can be output before PHP sends the HTTP headers, which should be the first thing sent to the browser. To solve this issue, make sure there are no spaces or characters outside the PHP tags <?php ?> and avoid any output (like echo, print, or whitespace) before sending headers. 

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

Keywords

PHP unnecessary spaces unnecessary characters headers already sent error

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