Sql query not running in php and maybe an issue related to sql

Question

Function is running properly and my other query of inserting data is also running perfectly which is commented below.
This is the error i am getting "Error: SELECT MAX(product_id) FROM product_attribute "

  public function add_tbl1($attribute_id , $attribute_description){
    $con=$this->con;
    $id = mysqli_real_escape_string($con, $attribute_id);
    $description = mysqli_real_escape_string($con, $attribute_description);
    $sql2="SELECT MAX(product_id) FROM product_attribute ";
    $no=0;


    if ($con->query($sql2) === TRUE) {
        $no= $con->query($sql2);
        $no=$no+1;
        echo $no;


    } else {
        echo "Error: " . $sql2 . "<br>" . $con->error;
    }   

    /*$sql = "INSERT INTO product_attribute ( attribute_id, attribute_description)
    VALUES ( '$id', '$description')";

    if ($con->query($sql) === TRUE) {
        echo "New record created successfully";
    } else {
        echo "Error: " . $sql . "<br>" . $con->error;
    }   */

    }

You need to show your SQL table layout because it might have a clue in there for us to tell you what is wrong. — Mark Manning
– Mark Manning, Commented Jan 21, 2016 at 7:07
You might want to take a look at en.wikipedia.org/wiki/SQL_injection#Hexadecimal_conversion. Look down at the hexadecimal conversion part. There is a PHP function there called dosql that you can use to - well - do SQL commands with and it returns various things. Just an idea. :-) — Mark Manning
– Mark Manning, Commented Jan 21, 2016 at 7:11

Franz Gleichmann · Accepted Answer · 2016-01-21 07:08:39Z

2

if $con is a mysqli-connection, then $con->query with a SELECT will never return true. it will either return false or a resource.

you should rather check with

 $con->query($sql2) !== false))

From http://php.net/manual/en/mysqli.query.php

Returns FALSE on failure. For successful SELECT, SHOW, DESCRIBE or EXPLAIN queries mysqli_query() will return a mysqli_result object. For other successful queries mysqli_query() will return TRUE.

answered Jan 21, 2016 at 7:08

Franz Gleichmann

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1 Comment

Abdur Rehman Farooqi Over a year ago

So how do i store id in a variable?

Hanky Panky · Accepted Answer · 2016-01-21 07:14:07Z

2

$con->query($sql2) === TRUE

mysqli::query does not return TRUE on success for SELECT statements. It returns

For successful SELECT, SHOW, DESCRIBE or EXPLAIN queries mysqli_query() will return a mysqli_result object

So change your if condition accordingly.

$sql2="SELECT MAX(product_id) as id FROM product_attribute ";
if ($result = $con->query($sql2)) {
    $row = $result->fetch_assoc();
    $id  = $row["id"];
}

edited Jan 21, 2016 at 7:14

answered Jan 21, 2016 at 7:08

Hanky Panky

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