php format date with 2 characters [duplicate]

Question 1

Your format is a bit ambigous, though I'm assuming since AM/PM isn't in there that the hours are in 24 hours format. Also not sure if the incoming date is day/month or month/day.

$date = new DateTime("3/6/2014 7:20");
echo $date->format('m/d/Y H:i');

Also not sure if the incoming date is day/month or month/day. But you can handle that with createFromFormat

$date = new DateTime::createFromFormat("n/j/Y G:i", "3/6/2014 7:20");
echo $date->format('m/d/Y H:i');

Read about date formats in the online docs. Also check out the DateTime book by the extension author to learn more.

Question 2

As simple as :)

date("m/d/Y h:i");

Refer to Manual to see what these values represent. Um, let me bring those here.

m = Numeric representation of a month, with leading zeros 
d = Day of the month, 2 digits with leading zeros
Y = A full numeric representation of a year, 4 digits
h = 12-hour format of an hour with leading zeros
i = Minutes with leading zeros

Question 3

Use the createFromFormat() function to read according to the specified format and output to the format you want.

http://www.php.net/manual/en/datetime.createfromformat.php

DateTime::createFromFormat -- date_create_from_format —
Returns new DateTime object formatted according to the specified format

Example:

$date = DateTime::createFromFormat('j/n/Y', '3/6/2014 G:i');
echo $date->format('m/d/Y h:i');