PHP putting “if” in header and “else” in footer

Each file included must be able to be parsed on its own without a syntax error. Your header has a syntax error of an unclosed if block. Likewise, the footer has a syntax error of an else block coming out of nowhere. You cannot do it this way.

Instead you can use something like:

// Global variable defined above includes:
$condition = TRUE;
include('header.php');
echo "The great brown fox jumps over the lazy dog.";
include('footer.php');


// header.php
if ($condition) {
  echo "hello world";
}

// footer.php
if (!$condition) {
  echo "bye";
}

Also using output buffing to grab content is way better then just including raw html into your code flow.

<?php 

function get_page_section($path){
    if(file_exists($path)){
        //grab "output" to the return variable
        ob_start();
        require($path);
        $return = ob_get_contents();
        ob_end_clean();
        return $return;
    }else{
        //path not found
        throw new Exception('get_page_section('.$path.') not found');
    }
}

$header = get_page_section('header.php');
$footer = get_page_section('footer.php');


echo $header.
     "The great brown fox jumps over the lazy dog.".
     $footer;

?>

in header.php type the following code

<?php
if(true){
    echo "Helloworld";
 }else{
     echo "bye bye";
     exit();
  }
?>

in the body.php continue as you wrote before

<?php
include('header.php');

echo "The great brown fox jumps over the lazy dog.";

this is the simplest way you can solve the probelm and hope this would help