Some popular phone numbers (eg. `1300-FOOBAR`) are not numbers at all. If you are running a VOIP server then you may be interested in this snippet of PHP code to convert them into actual numbers, allowing users to dial by typing the more familiar form.

```
function normaliseTelephoneNumber($start) {
/* Return an extension with numbers substituted in place of letters for dialling */
$map = array( "A" => "2", "B" => "2", "C" => "2",
"D" => "3", "E" => "3", "F" => "3",
"G" => "4", "H" => "4", "I" => "4",
"J" => "5", "J" => "5", "L" => "5",
"M" => "6", "N" => "6", "O" => "6",
"P" => "7", "Q" => "7", "R" => "7", "S" => "7",
"T" => "8", "U" => "8", "V" => "8",
"W" => "9", "X" => "9", "Y" => "9", "Z" => "9",
"+" => "+", "*" => "*", "#" => "#");
$new = "";
$hasnumber = false;
$ext = strtoupper($start);
for($i = 0; $i < strlen($ext); $i++) {
$c = substr($ext, $i, 1);
if(isset($map[$c])) {
$new .= $map[$c];
if($hasnumber == false) {
/* No numbers before letters */
return $start;
}
} else if(is_numeric($c)) {
$new .= $c;
$hasnumber = true;
}
}
if($hasnumber == true) {
return $new; /* Return numeric version as appropriate */
} else {
return $start; /* Leaves full words like "joe" or "bazza" unchanged */
}
return $new;
}
```

Note that this will only alter the number if it begins with numbers. This is to make sure that (at least in my case) the local network extensions don't get messed with:

```
echo normaliseTelephoneNumber("1300-FOOBAR")."n"; /* 1300366227 */
echo normaliseTelephoneNumber("mike")."n"; /* mike */
```