ereg / preg_match time validation

[Schmoopy]

Hi, I want to validate the time the user has entered to see whether it's in the correct format (12 hour format).

From googling around I found:

# Returns time in HH:MM[AM|PM] format if it matches, else false
function checkTime($time)
{
return (preg_match('/[\s0]*(\d|1[0-2]):(\d{2})\s*([AaPp][Mm])/xms', $time, $match))
? sprintf('%02d:%d%s', $match[1], $match[2], strtoupper($match[3]))
: false;
} 

It almost works, but it allows 21:50pm, I don't have any knowledge of ereg / preg_match so I'm finding it hard to alter it to fix it.

Anyone know what I need to do to fix it? Or come up with a better solution?

Thanks.

[techietim]

<?php
/*
VALID:
02:57am
12:53PM

INVAID:
2:57am
05:15 PM
13:11Pm
12:00aM
*/
function check_12hour_time($str){
    preg_match('/^(0[1-9]|1[0-2]):(0[1-9]|[1-5][0-9])(AM|PM|pm|am)$/', $str, $matches);
    return !$matches ? false:array('hours' => $matches[1], 'minutes' => $matches[2], 'tod' => $matches[3]);
}
var_dump(check_12hour_time('11:59PM'));

[Schmoopy]

That works great, thanks!

[JasonDFR]

<?php

$time = '21:50PM';

// Returns 1 if valid, 0 if not valid, false if $time hasn't been set
function check12Hour($time = null) {

if (!$time)
    return false;

return preg_match('/^(0[1-9]|1[0-2]):([0-5][0-9])(AM|PM)$/', $time);

}

echo check12Hour($time);

?>

I'm no expert with regex, but I am slowly getting better.

I think the trick is to build them one step at a time, testing it out as you go.

For example:

Start out with an idea of what valid is. In this case 09:00AM is valid.

Set up the format: '//'

Then go step by step:

'//'

'/^09:00AM$/' // ^ means starts with, $ means ends with

// The first "group" is the first two digits of the time
// Parenthesis around a group
// Now think about all possible values for the first two digits
// You can have a 0 followed by a 1-9 OR a 1 followed by a 0-2
// 0 followed by a 1-9 is written 0[1-9]
// Use | ( the pipe char ) for OR

'/^(0[1-9]|1[0-2]):00AM$/'

// Next you want a single colon, so type that.

// Then move on to the next group
// Parenthesis and follow the same idea as before

'/^(0[1-9]|1[0-2]):([0-5][0-9])AM$/'

// Then the AM OR PM gets some parenthesis

'/^(0[1-9]|1[0-2]):([0-5][0-9])(AM|PM)$/'

// And that's it

'/

[JasonDFR]

On yeah, one more thing I forgot to mention. If you are programming PHP forget you ever heard about ereg.

[Schmoopy]

@techietim - Your function almost worked , but didn't allow times like 05:00pm, or just any time with 2 0s for the minutes.

@JasonDFR - Thanks for your explanation, I've tested all my extremes and different values and so far all have passed, lucky you replied too

Thanks to both of you. Kudos.

[edit] And yes I did hear that ereg was being replaced by preg_match, since it's much faster and something else I can't remember, I only use it because I'm not very good at matches but I should spend some more time learning patterns as it seems really important when it comes to good validation.

[JasonDFR]

Cool,

I'm confident the function I posted will work for you.

I realized techie didn't quite get it right. His problem was (0[1-9]|[1-5][0-9]) which would be ok for 01 - 09 OR 10 - 59, but not 00.

I'm not sure why he did that. What was your thinking Techie?

[techietim]

I'm not sure why he did that. What was your thinking Techie?

Whoops

I was half asleep when I wrote that, so please excuse me.

[JasonDFR]

hehe, No worries. That kinda thing happens to me when I'm wide awake.

[Schmoopy]

Still guys, thanks for helping out - I'm getting so confused here converting 12 hour time to 24 hour for the database and then converting it back again for the user xD