PHP Warning: session_start(): Cannot start session when headers already sent in /home/readyj3a/public_html/makeup/admin/en/includes/applicationtop.php code example

Example: session_start(): cannot start session when headers already sent

// FIRST line of each php file using session (no character before)
<?php if ( empty(session_id()) ) session_start(); ?>
// Encode in ANSI or UTF8 (No BOM !)