php include function leaves my page blank -

when try include php menu and/or footer onto page, whole page shows blank. if take same code , put index.php html works fine. doing wrong?

here's index page:

<div id="navigation"> <?php include 'menu.php'; ?>         </div>     <div id="content"> <?php     echo "hello world!"; ?> </div>     <div id="footer">     <?php include 'footer.php'; ?>     </div> 

ok , here's menu.php , footer.php pages: menu:

<?php echo "<ul>     <li><a href="index.php">main</a></li>     <li><a href="info.php">php info</a></li>     <li><a href="wda1.php">assignment 1</a></li>     </ul>";     ?> 

footer:

<?php     echo "$filename = 'index.php';         if (file_exists($filename)) {         echo "this page last modified: " . date ("f d, y h:i:s.", filemtime($filename)); }";         ?> 

the tutorial @ http://www.w3schools.com/php/php_includes.asp lead me believe i'm doing correctly, apparently not case. appreciated, thank you.

here:

first file: (index.php presume?)

<div id="navigation"> <?php include 'menu.php'; ?>         </div>     <div id="content"> <?php     echo "hello world!"; ?> </div>     <div id="footer">     <?php include 'footer.php'; ?>     </div> 

menu:

<?php echo '<ul>     <li><a href="index.php">main</a></li>     <li><a href="info.php">php info</a></li>     <li><a href="wda1.php">assignment 1</a></li>     </ul>';     ?> 

footer:

<?php  echo $filename = 'index.php';    if (file_exists($filename)) {     echo "this page last modified: " . date ("f d, y h:i:s.", filemtime($filename)); }  // else not required show nothing if file doesn't exit // can remove it, it's optional else{ echo "<br>this not index.php. still show filename above this."; }  ?> 

---

here summary of mistakes made:

1) echo "<ul><li><a href="index.php">main</a></li>

• you either escape double quotes \" hyperlinks, or wrap echo using single quotes shown in answer above; it's lot less work.

then:

2) echo "$filename = 'index.php'; ... }";

• you're wrapping entire code in double quotes, hoping that; echo. generate parse error, carbon copy of did in point #1.
• removing first double quote before $filename getting rid of last 1 }";

---

troubleshooting tip(s)

add error reporting top of file(s) error_reporting(e_all); ini_set('display_errors', 1); signal errors found in code , guide along.

for more information on error reporting, visit php.net:

• http://www.php.net/manual/en/function.error-reporting.php