MYSQL Query with String Refer to Value in Database

Question

I have MYSQL query like the below:

$sourcedata = mysql_fetch_array(
                mysql_query("SELECT Whereclause 
                               FROM generaltable 
                              WHERE ID = '1'"
                           )
                );

$Whereclause = $sourcedata['Whereclause'];

In "Whereclause" field from "generaltable" in database, consist of the below text:

WHERE username = '$_SESSION[username]'

Then I have other query:

$data = mysql_fetch_array(
                   mysql_query("SELECT * 
                                  FROM usertable 
                                       $Whereclause"
                              )
                        );

When I echo $data['username'], it is not showing anything.

If I copy the value from database to replace $Whereclause it is working fine, also if I replace '$_SESSION[username]' with 'admin' for example, it is working fine.

How can I solve this? Need your help please.

Thank you very much.

try to print "SELECT * FROM usertable $Whereclause" and query it in your mysql editor — Pantamtuy
– Pantamtuy, Commented Oct 17, 2014 at 8:24
@Pantamtuy Do you mean from sql query in phpmyadmin? Can it identify the $Whereclause? — anesbbs
– anesbbs, Commented Oct 17, 2014 at 8:53

vineet verma · Accepted Answer · 2014-10-17 08:20:15Z

1

As you are using fetch array. Can you please try with

$data[0]['username']

answered Oct 17, 2014 at 8:20

vineet verma

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Comments

Oscar Pérez · Accepted Answer · 2014-10-17 12:00:53Z

0

The problem you're having is that $Whereclause is a String, so it is not evaluated ('$_SESSION[username]' remains exactly as it is).

You have to tell PHP to evaluate this string with the function eval():

$data = mysql_fetch_array(
          mysql_query(
           eval("return \"SELECT * FROM usertable $Whereclause\";")
         )
        );

edited Oct 17, 2014 at 12:00

answered Oct 17, 2014 at 8:08

Oscar Pérez

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2 Comments

anesbbs Over a year ago

Warning: mysql_fetch_array() expects parameter 1 to be resource, boolean given in ...

Oscar Pérez Over a year ago

True! I'm going to correct it, look back the answer in a minute

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