CODEWITHSUNDEEP
phpmysql
Kriz
Kriz

Reputation: 27

Querying MySQL database using PHP (if statement)

I need your help.

I have a PHP code that I use to query a MySQL database after selecting a certain operator. The operators that I have from the dropdown list are "LESS THAN, GREATER THAN, and EQUALS". The problem I have is; whichever operator I select, the result that I get from the database is always for the "LESS THAN" operator. That is, it give me the same result whether I select "LESS THAN", "GREATER THAN" or "EQUALS". I tried to locate the problem but failed. Here is the code that I use:

            if ($op='LESS THAN') {
        $query = "SELECT * FROM tbl_reservoir WHERE res_vol < '$vol'";
    } elseif ($op='GREATER THAN') {
            $query = "SELECT * FROM tbl_reservoir WHERE res_vol > '$vol'";
    } elseif ($op='EQUAL') {
         $query = "SELECT * FROM tbl_reservoir WHERE res_vol = '$vol'";
    }

$op is a variable that holds the operator, and "res_vol" is a field that I compare with from the database table.

Upvotes: 1

Views: 866

Answers (2)

Ross Smith II
Ross Smith II

Reputation: 12189

You're using an assignment operator (=) where you want the equality operator (==), so your code should read:

        if ($op=='LESS THAN') {
    $query = "SELECT * FROM tbl_reservoir WHERE res_vol < '$vol'";
} elseif ($op=='GREATER THAN') {
        $query = "SELECT * FROM tbl_reservoir WHERE res_vol > '$vol'";
} elseif ($op=='EQUAL') {
     $query = "SELECT * FROM tbl_reservoir WHERE res_vol = '$vol'";
}

but, you could simplify this to:

static $map = array('LESS THAN' => '<', 'GREATER THAN' => '>', 'EQUAL' => '=');
if (!isset($map[$op])) {
    throw new Exception(sprintf("Unexpected operator '%s', $op));
}
$query = sprintf("SELECT * FROM tbl_reservoir WHERE res_vol %s '$vol'", $map[$op]);

Upvotes: 1

John Woo
John Woo

Reputation: 263933

You have to use == or === in your if condition

if ($op == 'LESS THAN')
{
  // code here
}
elseif ($op == 'GREATER THAN')
{
  // code here
}
// .......

Upvotes: 1

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