PHP form validation where value is not null

Answer

Solution:

maybe you want to use empty() function on strlen() function because is_null() checks NULL value. If $postcode is == "" it's not NULL.

http://php.net/manual/en/function.is-null.php
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than you can use

else if(!empty($postcode) && !is_numeric($postcode))  {
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or

else if(strlen($postcode) > 0 && !is_numeric($postcode))  {
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or

else if($postcode != "" && !is_numeric($postcode))  {
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As specified in the link, if you want to use is_null, is better to use $postcode !== NULL. Much faster

Answer

Solution:

Assuming$postcode comes from either a$POST or$GET, it always is a string.!is_null() will, therefore be FALSE, regardless:

php> var_dump(is_null(""))
#=> bool(false)
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You could revert to usingempty(), which is more liberal. However, PHP is utterly inconsistent and weird when it comes to these checks. For example,empty() will returnFALSE for 0 too. Yup.

php> $postcode = "";
php> var_dump(empty($postcode))
#=> bool(true)
php> $postcode = 0;
php>var_dump(empty($postcode))
#=> bool(true)
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A much better approach, is to do some sort of "duck-typing". In your case: when it can be converted to a numeric value, do that and use it. Then leave it to the language to determine what it considers "number-ish" enough to convert.

php> var_dump((int) "")
int(0)
php> var_dump((int) "13")
int(13)
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So:

else if(($postcode = (int) $postcode) && ($postcode > 0)) {
}
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And last, off-topic: a heed of warning about your business assumptions: postcodes are not always numeric. Yes, in the US most are. But there are more countries out there (saying this as a EU-citizen who comes way too often about sites that assume everyone is an average-US-citizen)

Answer

Solution:

Try this

else if(!empty($postcode) && !is_numeric($postcode))  {
  $msg_to_user = '<br /><br /><h4><font color="FF0000">Postcode must be a numeric value.</font></h4>';
}
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Hope this helps