PHP - ob_start example

Example 1
    
        ob_start(); // captures the output and save it in an internal buffer
        echo("world!"); // "world!" saved in internal buffer
        $output = ob_get_contents(); // save in a variable internal buffer content
        ob_end_clean(); // clean internal buffer
        echo 'Hello ' . $output;
        // output
        // Hello world!
    
Example 2
    
        ob_start();
        echo("Hello world!");
        $output = ob_get_contents();
        ob_end_flush(); // print internal buffer content
        // output
        // Hello world!