How can I create a php function out this date validation code?

Question

I have piece of code that works without making it a function. But, when I make it a function, it always returns false. The purpose of this function is to check if the date is valid, as the name suggests. Can anybody tell me what is wrong with the code ?

function is_valid_date($a) {
//date format Y-m-d H:i:s
if(preg_match('/^((19|20)\\d\\d)-(0?[1-9]|1[012])-(0?[1-9]|[12][0-9]|3[01]) ([01]\d|2[0123]):([0-5]\d):([0-5]\d)$/', $a)){ 
    list( $_date , $_time ) = explode(' ',$a);
    list ($year,$month,$day) = explode("-",$_date);
    list($hour,$minute,$second) = explode(":",$_time);

    if ($day == "31" && ($month == "4" || $month == "6" || $month == "9" || $month == "11" || $month == "04" || $month == "06" || $month == "09" ))  {
        return false;
    } elseif ($month == "2" || $month == "02") {
            if($year % 4==0){
                if($day == "30" || $day == "31"){
                    return false;
                } else {
                    return true;
                }
            }else{
                if($day == "29" || $day == "30" || $day == "31"){
                    return false;
                } else {
                    return true;
                }
            }
    }

}else{
    return false;

}
}

when I try

if (is_valid_date("2012-12-02 15:30:00")) { echo "valid date";}

nothing is printing.

I see that your function can return true only else if month=2 — Andrew
– Andrew, Commented Dec 1, 2012 at 21:28
why write your own date validation routine when PHP has it all built-in already? — Spudley
– Spudley, Commented Dec 1, 2012 at 21:31

h2ooooooo · Accepted Answer · 2012-12-01 21:29:14Z

1

What's wrong with the following using checkdate?

<?php
    function is_valid_date($date) {
        if (preg_match('/^((19|20)\\d\\d)-(0?[1-9]|1[012])-(0?[1-9]|[12][0-9]|3[01]) ([01]\d|2[0123]):([0-5]\d):([0-5]\d)$/', $date, $matches)){
            return checkdate($matches[3], $matches[4], $matches[1]);
        }
        return false;
    }
    var_dump(is_valid_date("2012-12-02 15:30:00")); //true
?>

This will match the following:

2012-10-13 00:00:00
1990-02-30 12:34:56

but not

15:30:00
2012-12-02
2012/12/02 15:30:00
2012-13-02 15:30:00

Click here to see it running online

answered Dec 1, 2012 at 21:29

h2ooooooo

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2 Comments

jinni Over a year ago

i guess this works exactly as intended. but what are $matches 3 4 and 1 ?

h2ooooooo Over a year ago

@jinni as you can see I've added a parameter of , $matches to the preg_match call. This means that everything in parenthesises gets "matched" and outputted in this $match array which now looks like the following (using print_r, from 2012-12-02 15:30:00): Array( [0] => 2012-12-02 15:30:00 [1] => 2012 [2] => 20 [3] => 12 [4] => 02 [5] => 15 [6] => 30 [7] => 00) meaning that the 3rd is the month, the 4th is the day and the 1st parameter is the year. You can see more on the preg_match manual page: php.net/manual/en/function.preg-match.php

jcjr · Accepted Answer · 2012-12-01 21:27:19Z

Put

return true;

before the end of the function (before the last brace } ). Otherwise in some cases, nothing is returned and it is considered false.

Whole code:

function is_valid_date($a) {
//date format Y-m-d H:i:s
if(preg_match('/^((19|20)\\d\\d)-(0?[1-9]|1[012])-(0?[1-9]|[12][0-9]|3[01]) ([01]\d|2[0123]):([0-5]\d):([0-5]\d)$/', $a)){ 
    list( $_date , $_time ) = explode(' ',$a);
    list ($year,$month,$day) = explode("-",$_date);
    list($hour,$minute,$second) = explode(":",$_time);

    if ($day == "31" && ($month == "4" || $month == "6" || $month == "9" || $month == "11" || $month == "04" || $month == "06" || $month == "09" ))  {
        return false;
    } elseif ($month == "2" || $month == "02") {
            if($year % 4==0){
                if($day == "30" || $day == "31"){
                    return false;
                } else {
                    return true;
                }
            }else{
                if($day == "29" || $day == "30" || $day == "31"){
                    return false;
                } else {
                    return true;
                }
            }
    }

}else{
    return false;

}
    return true;

}

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