如何在php [duplicate]中删除警告“mysql_num_rows（）期望参数1为资源”

Question

This question already has an answer here:

• Reference - What does this error mean in PHP? 34 answers

I make a php page in which i want to get data from database but when i run it gives me the warning "mysql_num_rows() expects parameter 1 to be resource".

How i remove this warning?

Here is my code:

$strQuery1 = "select DATE_FORMAT(transactions.transaction_date,'%m-%d-%Y') as transaction_date,sum(amount)as Amount from transactions where event_id='7' group by  DATE_FORMAT(transactions.transaction_date,'%m-%d-%Y')";
$result1 = $GLOBALS ['mysqli']->query ($strQuery1) or die ($GLOBALS ['mysqli']->error . __LINE__);
$rows=mysql_num_rows($result1);
while($rs1=$result1->fetch_assoc()){    
    $res1[]=$rs1;                   
}
for ($i = 0 ; $i <=30 ; $i++) {
    foreach($res1 as $r){
        if($r['transaction_date']==$dates[$i]){
            $substrXML1= "<set value='" . $r['Amount'] ."' />";
            break;
        } else
           {
            $substrXML1= "<set value='0' />";
        }
    }
        $strXML1 .=$substrXML1;
}
    $strXML1.="</dataset>";

</div>

Answer 1

$rows=mysqli_num_rows($result1);