Take the following code:

public class phptest{
  public static String testString = "look for ^ in this string";

public static void main(String[] args)
{
 System.out.println("Found ^ at: "+testString.indexOf('^'));
}
}

Which when run in Java produces this output:
Found ^ at: 9

Now, consider the following php code:
<?php

$phptest = new Java("phptest");

printf("Found ^ at: %d\n", $phptest->$testString->indexOf('^'));
?>

This *almost* works, and produces the following output:
X-Powered-By: PHP/4.0.6
Content-type: text/html

<br>
<b>Warning</b>:  java.lang.NoSuchMethodException: indexof in <b>phptest.php</b> on line <b>5</b><br>
Found ^ at: 0

As you can see, the indexof method has been lowercased from indexOf.  This is a problem in the case sensitive environment of Java.