How does one verify that the input date is a valid date? Here is an example (checkdate. php3

Htmlbody? Functionis_numeric ($ var) {$ str (string) $ var; $ int (int) $ var; $ strstr (string) $ int; if ($ strstr $ str) returntrue; elsereturnfalse;} functioncheck ($ year, $ month, $ day)

Function is_numeric ($ var ){
$ Str = (string) $ var;
$ Int = (int) $ var;
$ Strstr = (string) $ int;
If ($ strstr = $ str) return true;
Else return false;
}

Function check ($ year, $ month, $ day)
{
If (is_numeric ($ year) and is_numeric ($ month) and is_numeric ($ day )){
If (checkdate ($ month, $ day, $ year )){
Echo $ year. "year". $ month. "month". $ day. "is the legal date!
";
}
Else {
Echo $ year. "year". $ month. "month". $ day. "The date is not a valid date!
";
}
}
Else {
Echo $ year. "year". $ month. "month". $ day. "The date is not a valid date!
";
}
}

Check ("1999", "1", "1 ");
Check ("2000", "2", "31 ");
Check ("1900", "2", "1 ");
Check ("1900.2", "2", "1 ");
Check ("aaa", "1", "1 ");
?>