Jeff Moore mentions a "sweet improvement" he noticed when comparing the error message from a PHP4 script to a PHP5 one - the location reported for error mesages.
Sometimes its the little things that make a difference.
His sample script (a function call without the argument needed) errors on the location of the function definition in PHP4, but happily PHP5 recognized the problem for what it's worth and echoed out the location of the call to that function instead for the line number.
One more reason to ditch PHP 4 and go php 5.
Jeff Moore's Blog: Improved Error Messages in PHP - Read More... 
