How can I make my code better and/or more efficient
<p>I'm trying to improve my PHP programming skills, can anyone give me any tips or direction based on this code that I wrote?</p>

<pre><code>&lt;?php

include("db.php");
include("function.php");

//variables
$number = htmlspecialchars($_POST['num']);
$date = date("Y-m-d");

//validate phone number
if (strlen($_POST['num']) != 12){
print "Invalid Phone Number.";
die();
}

//check how many times the number was called today

    $callstoday = mysql_query("
    SELECT number
    FROM numbers 
    WHERE number = '$number'
    AND date 
    LIKE '$date%'")
    or die(mysql_error());
    $callstotal = mysql_num_rows($callstoday);



//cant do more than 5 calls

 if ($callstotal &lt; 5){
  //do nothing
 }else{
  print "Not Allowed";
 die();
 }





//break up the number in 3 parts
$bits = explode("-", $number);
$data = get_carrier("http://site.com/?action=carrierlookup&amp;p1=".$bits[0]."&amp;p2=".$bits[1]."&amp;p3=".$bites[2]."&amp;iecache=0");


//check when they want to call

if ($_POST['when'] == 'now' ){
$when = "0";
}elseif($_POST['when'] == 'secs'){
$when = "30";
}elseif($_POST['when'] == 'minute'){
$when = "60";
}elseif($_POST['when'] == '2minute'){
$when = "120";
}elseif($_POST['when'] == '5minute'){
$when = "300";
}

//check for carrier
if(strstr($data, 'Cingular')){
$carrier = "AT&amp;T";
}elseif(strstr($data, 'Sprint')){
$carrier = "Sprint";
}elseif(strstr($data, 'Verzion')){
$carrier = "Verzion";
}elseif(strstr($data, 'T-Mobile')){
$carrier = "T-Mobile";
}elseif(strstr($data, 'Boost')){
$carrier = "Boost Mobile";
}elseif(strstr($data, 'Cricket')){
$carrier = "Cricket";
}elseif(strstr($data, 'Alltel')){
$carrier = "Alltel";
}elseif(strstr($data, 'Unable')){
$carrier = "Unknown Carrier";
}




//inset number and carrier into database.
mysql_query("INSERT INTO numbers (number, carrier)
VALUES ('$number', '$carrier')");
print "success";
mysql_close($con);


//call out to the number
$strippednumber = str_replace("-", "", $number);
$call = call("http://domain.com");


?&gt;
</code></pre>
