Determine if a variable is numeric

There are a number of ways to determine if a variable in PHP is numeric. If you have PHP 4, you can use the is_numeric function:

if (is_numeric($thefield)==false) {
  echo "\$thefield is not a number";

If you have PHP 3, then you can use the following function

function is_numeric($value) {
  if (((int) $value)== $value) {
    return true;
  } else {
    return false;

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