PHP - Pdo::execute Returning False

<?php
$db_host = "localhost";
$db_user ="root";
$db_pass ="";
$db_database ="allscores";

//////////////// CHECKING VARIABLE FILEDS IN A UPDATE QUERY //////////////////////////////////
//////////////// QUERY 1 /////////////////////////////////////////////////////////////////////

/*
$db_database ="test";
$db_table ="users";
$RecNo = 1;			
		
$field1 = 'name';
$field2 = 'password';
$field3 = 'email'; 
$field4 = 'id';
$val1 = "Ajay";
$val2 = "howzatt";
$val3 = "me@mymail.com";


					$con = mysqli_connect($db_host,$db_user,$db_pass,$db_database) or die('Unable to establish a DB connection');
					$query = "UPDATE $db_table SET $field1 = ?,
							$field2 = ?, $field3 = ?
							WHERE $field4 = ? ";   // session terminated by setting the sessionstatus as 1 
					$stmt = $con->prepare($query);
					var_dump($stmt); 
					$stmt->bind_param('sssi',$val1,$val2,$val3,$RecNo);
					if($stmt->execute())
					{
						$count = $stmt->affected_rows;
						echo $count;
					}		
//////////////// QUERY 1  END /////////////////////////////////////////////////////////////////////
*/



//////////////// QUERY 2 /////////////////////////////////////////////////////////////////////

$con = mysqli_connect($db_host,$db_user,$db_pass,$db_database) or die('Unable to establish a DB connection');
$table = 'scores';
$date = date('Y-m-d H:i:s');


/*
$prestr 	= "Mrt_M_";		
$STATUS		= $prestr."Status";
$S_R1 		= $prestr."Scr_1";
$S_R2 		= $prestr."Scr_2";
$PCT 		= $prestr."PPT";
$DPM 		= $prestr."DSP";
$TIMETAKEN 	= $prestr."TimeTaken";
*/


$STATUS		= "Mrt_M_Status";
$S_R1 		= "Mrt_M_Scr_1";
$S_R2 		= "Mrt_M_Scr_2";
$PPT 		= "Mrt_M_PPT";
$DSP 		= "Mrt_M_DSP";
$TIMETAKEN 	= "Mrt_M_TimeTaken";

$TimeOfLogin	=	$date;	
$no_of_logins	=	10;
$time_of_nLogin	=	$date;
$m_scr_row1		=	5;
$m_scr_row2		=	5;
$m_ppt			=	20;
$m_dsp			=	60;
$m_time			=	120;
$date			=	$date;
$RecNo			=	24;

		$query = "UPDATE $table SET 
				TimeOfLogin = ?,
				no_of_logins = ?,
				time_of_nLogin = ?,
				$S_R1 = ?,					
				$S_R2 = ?,					
				$PPT = ?,						
				$DSP = ?,						
				$TIMETAKEN = ?,				
				$STATUS = '1',				
				TimeOfLogout = ?,
				WHERE RecNo = ?";			
		$stmt = $con->prepare($query);

		var_dump($stmt);

		$stmt->bind_param('sisiiddssi',$TimeOfLogin,$no_of_logins,$time_of_nLogin,$m_scr_row1
					$m_scr_row2,$m_ppt,$m_dsp,$m_time,$date,$RecNo);
		if($stmt->execute()) echo " DONE !";


?>	

int strpos(char s[], char t[])
{
    int i, j, k;

    for (i = 0; s[i] != '\0'; i++) {
        for (j=i, k=0; t[k]!='\0' && s[j]==t[k]; j++, k++)
            ;

        if (k > 0 && t[k] == '\0')
            return i;
    }

    return -1;
}