PHP - Two Queries And A Variable From One To The Other

Good day everyone. I go by the nickname Sbosh and I am a newbie in PHP.

I am currently learning php using video tutorials. I need help with regards to php queries.

I have the following code:

"SELECT 'food', 'calories' FROM 'diet' ORDER BY 'id'"

which is supposed to display content from a table inside phpmyadmin which i created manually using phpmyadmin. But It gives an error saying i must check the MariaDB version on how to right this query, something like that.

Please assist on the proper way of writing this code. Again I am a newbie in PHP and just starting to learn, so your help will be highly appreciated.

<?php
function childtheme_cat_limited_blog( $query ) {
    if ( $query->is_home() && $query->is_main_query() ) {
        $query->set( 'events_categories', 'mycategory1' );
    }
}
add_action( 'pre_get_posts', 'childtheme_cat_limited_blog' );
?>

<?php
function childtheme_cat_limited_blog( $query ) {
    if ( $query->is_home() && $query->is_main_query() ) {
        $query->set( 'category_name', 'mycategory2' );
    }
}
add_action( 'pre_get_posts', 'childtheme_cat_limited_blog' );
?>

/* No filtering and no unread */
$q_urls = "SELECT * FROM shortenified_urls WHERE is_social = '1' AND active = '1' ORDER BY date_added DESC";

/* All links in a particular category */
$q_urls = "
SELECT * FROM shortenified_urls
WHERE shortenified_urls.primary_cat = $vu_cat_view
OR EXISTS (
SELECT link_id FROM linkcats
WHERE link_id = shortenified_urls.id AND cat_id = $vu_cat_view
)
AND shortenified_urls.is_social = '1' AND shortenified_urls.active = '1'
ORDER BY date_added DESC"
;

/* Unread only for all categories */
$q_urls = "SELECT * FROM shortenified_urls
WHERE shortenified_urls.date_added > $vu_mark_as_read
AND NOT EXISTS (
SELECT lid FROM linkviews
WHERE lid = shortenified_urls.id AND uid = $viewing_user_id
)
AND shortenified_urls.is_social = '1' AND shortenified_urls.active = '1'
ORDER BY date_added DESC"
;

/* Unread links in a particular category */
$q_urls = "
SELECT * FROM shortenified_urls
WHERE shortenified_urls.primary_cat = $vu_cat_view AND shortenified_urls.date_added > $vu_mark_as_read
OR EXISTS (
SELECT link_id FROM linkcats
WHERE link_id = shortenified_urls.id AND cat_id = $vu_cat_view
)
AND NOT EXISTS (
SELECT lid FROM linkviews
WHERE lid = shortenified_urls.id AND uid = $viewing_user_id
)
AND shortenified_urls.is_social = '1' AND shortenified_urls.active = '1'
ORDER BY date_added DESC"
;

$Actv = 0;
$ActvCount = -1;
$ActvUpgrade = 0;
$ActvRenewal = 0;
$ActvVehicleAdds = 0;

$result2 = mysql_query("SELECT * FROM tblOperators WHERE OperatorLocale = 'USA' and OperatorStatus = 'ACTIVE' and Team = 'RENEWALS'");
while($row2 = mysql_fetch_array($result2)) {
 $operID = $row2['OperatorID'];
 
 $result = mysql_query("SELECT * FROM tblUserPayments WHERE OperatorID = '$operID' AND PaymentStatus='OK' AND PaymentDate LIKE '$currentDate%'");

 while($row = mysql_fetch_array($result))
 {
	if($row['PaymentReason'] == 'ACTIVATION'){
		++$ActvCount;
		//if($row['PaymentMethod'] == 'CREDITCARD'){
			$ActvUpgrade += $row['ChargeAmount'];
		//}
	}

	elseif($row['PaymentReason'] == 'UPGRADE'){
		$userid = $row['UserID'];
		$paymentdate = $row['PaymentDate'];
		$result1 = mysql_query("SELECT * FROM tblRenewalInvoices WHERE UserID='$userid' AND ('$paymentdate' >= DATE_SUB(DueDate, INTERVAL 90 DAY) AND '$paymentdate' < DATE_ADD(DueDate, INTERVAL 15 DAY)) AND ParentInvoiceID IS NULL ORDER BY InvoiceNum DESC LIMIT 1");
		if( $row1 = mysql_fetch_array($result1)) {
			$packageid = $row['PackageID'];
			$pack = mysql_query("SELECT * FROM tblUserPackages WHERE PackageID='$packageid';");
			if($pack1 = mysql_fetch_array($pack)){

				$expDate = $pack1['ExpirationDate'];
				$dueDate = $row1['DueDate'];
				$days = mysql_fetch_row(mysql_query("SELECT TO_DAYS('$expDate')-TO_DAYS('$dueDate');"));
				$months = (int)( ((int)$days + 14) / 30.4);
				$years = (int) ( ((int)$days + 182) / 365);
				$Intervals = 0;
				if($years > 0){
					$Intervals = $years;
				}
				if(($pack1['Package'] or 'GPS-SVL') or ($pack1['Package'] == 'GPS-1') or ($pack1['Package'] == 'GPS-1PLUS')){
					if($Intervals > 1){
						//if($row['PaymentMethod'] == 'CREDITCARD'){
							$Actv += $row['ChargeAmount'];
						//}
					}
					else{
						//if($row['PaymentMethod'] == 'CREDITCARD'){
							$ActvRenewal += $row['ChargeAmount'];
						//}
					}
				}
				else{
					$Actv += $row['ChargeAmount'];
				}
			}
			else{
			}
		}
		else{
			//if($row['PaymentMethod'] == 'CREDITCARD')
				$ActvUpgrade += $row['ChargeAmount'];
		}
	}

	elseif($row['PaymentReason'] == 'ADDVEHICLE'){
		//if($row['PaymentMethod'] == 'CREDITCARD')
			$ActvVehicleAdds += $row['ChargeAmount'];
	}
		
 }

$result = mysql_query("SELECT * FROM tblRenewalCalls WHERE OperatorID = '$operID' AND PayStatus='OK' AND DateSubmitted LIKE '$currentDate%'");

 while( $row = mysql_fetch_array($result) )
 {
	if($row['Charged']){
		if ((int)$row['RenewYears'] > 1) {
			$Actv += $row['RenewTotal'];
		}
		else{
			$ActvRenewal += $row['RenewTotal'];
		}
	 }
  }
 }
$total = $Actv+$ActvRenewal+$ActvUpgrade+$ActvVehicleAdds;

$ActvRenewal = $total - ($ActvVehicleAdds + $ActvUpgrade);

$upgradeEarned = $ActvUpgrade;
$renewalEarned = $ActvRenewal;

$query1 = "SELECT * FROM forums WHERE MATCH (topics) AGAINST ('$keywords' IN BOOLEAN MODE)";

$query2 = "SELECT * FROM users WHERE username='$username";