here's a neat little function I whipped up to do HTML color coding of SQL strings. 
<?php
function SQL_DEBUG( $query )
{
    if( $query == '' ) return 0;
    global $SQL_INT;
    if( !isset($SQL_INT) ) $SQL_INT = 0;
    $query = preg_replace("/['\"]([^'\"]*)['\"]/i", "'<FONT COLOR='#FF6600'>$1</FONT>'", $query, -1);
    $query = str_ireplace(
                            array (
                                    '*',
                                    'SELECT ',
                                    'UPDATE ',
                                    'DELETE ',
                                    'INSERT ',
                                    'INTO',
                                    'VALUES',
                                    'FROM',
                                    'LEFT',
                                    'JOIN',
                                    'WHERE',
                                    'LIMIT',
                                    'ORDER BY',
                                    'AND',
                                    'OR ', 'DESC',
                                    'ASC',
                                    'ON '
                                  ),
                            array (
                                    "<FONT COLOR='#FF6600'><B>*</B></FONT>",
                                    "<FONT COLOR='#00AA00'><B>SELECT</B> </FONT>",
                                    "<FONT COLOR='#00AA00'><B>UPDATE</B> </FONT>",
                                    "<FONT COLOR='#00AA00'><B>DELETE</B> </FONT>",
                                    "<FONT COLOR='#00AA00'><B>INSERT</B> </FONT>",
                                    "<FONT COLOR='#00AA00'><B>INTO</B></FONT>",
                                    "<FONT COLOR='#00AA00'><B>VALUES</B></FONT>",
                                    "<FONT COLOR='#00AA00'><B>FROM</B></FONT>",
                                    "<FONT COLOR='#00CC00'><B>LEFT</B></FONT>",
                                    "<FONT COLOR='#00CC00'><B>JOIN</B></FONT>",
                                    "<FONT COLOR='#00AA00'><B>WHERE</B></FONT>",
                                    "<FONT COLOR='#AA0000'><B>LIMIT</B></FONT>",
                                    "<FONT COLOR='#00AA00'><B>ORDER BY</B></FONT>",
                                    "<FONT COLOR='#0000AA'><B>AND</B></FONT>",
                                    "<FONT COLOR='#0000AA'><B>OR</B> </FONT>",
                                    "<FONT COLOR='#0000AA'><B>DESC</B></FONT>",
                                    "<FONT COLOR='#0000AA'><B>ASC</B></FONT>",
                                    "<FONT COLOR='#00DD00'><B>ON</B> </FONT>"
                                  ),
                            $query
                          );
    echo "<FONT COLOR='#0000FF'><B>SQL[".$SQL_INT."]:</B> ".$query."<FONT COLOR='#FF0000'>;</FONT></FONT><BR>\n";
    $SQL_INT++;
} ?>