Problems with function

[rocky_88]

I am trying to check whether a given value exists in the database or not before inserting/deleting/updating it.

So i will be doing it using 4 functions, one is to check if the record exists and other 3 to add, update & delete.

 

Here is a sample code

 

function check($k)
{
$chk="select * from tablename where columnname = '$k'";
$res=mysql_query($chk);
$count = mysql_num_rows($res);
if ($count>0)
{
return false;
}
}

function add($a)
{
$sql="insert into tablename values('$a')";
$exec = mysql_query($sql);
if($exec)
{
echo "row added successfully";
}
else
{
echo "could not update table";
}
}

 

How do i control the add function on the basis of the output of the check function?

[KevinM1]

Try:

 

if (!check($value)) { add($value); }

[rocky_88]

@Nightslyr

 

Thanks for replying,

I should had mentioned this earlier, sorry about that.

I want to call the check function within the add function.

I'm using classes and hence all these functions will be on a different page and i'll be calling only add/delete/update function and hence want to include the check function within these three functions.

[KevinM1]

function add($value)
{
   if (!check($value)) // when you translate this to a class, you'll have to use !$this->check($value)
   {
      // add the value
   }
   else
   {
      // abort, because the value already exists
   }
}

 

You may want to give check() a better name, like valueExists(), just so your code is more readable.

[rocky_88]

Thanks for the reply & suggestion,

tried the code (!$this->check($value)), but it did not work,

it is adding duplicate values.

 

 

[KevinM1]

Show me your actual code.

[rocky_88]

Its almost the same as above,

here

function check($k)
{
$chk="select * from testing where username = '$k'";
$res=mysql_query($chk);
$count = mysql_num_rows($res);
if ($count>0)
{
return false;
}
}

function add($a)
{
if (!$this->check($a))
{
$sql="insert into testing values('$a')";
$exec = mysql_query($sql);
if($exec)
{
echo "row added successfully";
}
else
{
echo "could not update table";
}
}
else
{
echo "Value exists, enter a different string";
}
}

[KevinM1]

Is this all of it?  As in, you don't have any code that defines a class?

[rocky_88]

Nope, that is just the function part.

This is the whole class page,

lemme know if u want the other page too.

<?php
class db_handling
{
function connection()
{
$con = mysql_connect("localhost","root","");
if(!$con)
{
die ("Connection Failed");
}
echo "Connected <br/>";
}

function selection()
{
$recordset = mysql_select_db ("sample");
if(!$recordset)
{
die ("Database not found");
}
echo "Database selected <br/>";
}

function check($k)
{
$chk="select * from testing where username = '$k'";
$res=mysql_query($chk);
$count = mysql_num_rows($res);
if ($count>0)
{
return false;
}
}

function add($a)
{
if (!$this->check($a))
{
$sql="insert into testing values('$a')";
$exec = mysql_query($sql);
if($exec)
{
echo "row added successfully";
}
else
{
echo "could not update table";
}
}
else
{
echo "Value exists, enter a different string";
}
}
?>

[KevinM1]

In check, put:

 

if ($count > 0) { return false; }
else { return true; }

[rocky_88]

@Nightslyr

 

Now its not at all taking any values,

for all the values it says Value exists.

 

It was working fine when i put the statements of the check function within add function, but if i call it as a function, its not working at all.

[KevinM1]

Try:

 

class DB_Handling
{
   private $dbconn;

   public function __construct($dbname)
   {
      $conn = mysql_connect("localhost", "root", "");

      if ($conn)
      {
         $this->dbconn = $conn;

         $recordset = mysql_select_db($dbname);

         if (!$recordset) { /* abort, error */ }
      }
      else { /* abort, error */ }
   }

   public function valueExists($value, $tablename)
   {
      $query = "SELECT * FROM $tablename WHERE username = $value";
      $result = mysql_query($query, $this->dbconn);
      $count = mysql_num_rows($result);

      if ($count > 0) { return false; }
      else { return true; }
   }

   public function add($value, $tablename)
   {
      if (!$this->valueExists($value, $tablename))
      {
         $query = "INSERT INTO $tablename VALUES ($value)";
         $result = mysql_query($query, $this->dbconn);

         if ($result) { echo "Success!"; }
         else { /* abort, query error */ }
      }
      else { /* abort, value exists */ }
   }
}

$myDB = new DB_Handling("sample");
$myDB->add("Bubba", "testing");

 

NOT tested, so there may be some syntax errors, and you'll need to fill in the error handling.

[rocky_88]

@Nightslyr

 

Thanks for the code,

But i still cant get it to work right,

I modified my own version of coding and there seem to be a problem while calling the function.

 

function check($k)
{
$chk="select * from testing where username = '$k'";
$res=mysql_query($chk);
$count = mysql_num_rows($res);
}

function add($a)
{
$this ->check($a);
echo $this ->count; // It doesnt not echo this, my guess is there is some problem at function call.
if ($this ->count<=0)
{
// Insert in to table
}
else
{
// Show error
}
}

[KevinM1]

$this->count doesn't exist.  $count is local to the check() method.  The 'this' keyword denotes a class member, which is either a pre-declared class field (like $dbconn was in my example), or a class method.  Local variables (variables created within a method) don't count, and unless they're returned and stored in a variable outside of that method's scope, essentially disappear, which is what $count does.

 

Before you go much further, you should brush up on the basics: http://php.net/manual/en/language.oop5.php

[rocky_88]

@Nightslyr

 

Thanks for the explanation & link.