PHP : Translate date/time format between `date()` and `strftime()`

composer.json

{
  "name": "joel-depiltech/date-format-conversion",
  "description": "Translate date/time format between `date()` and `strftime()`",
  "authors": [
    {
      "name": "Chauncey McAskill",
      "email": "chauncey@mcaskill.ca",
      "homepage": "https://github.com/mcaskill"
    },
    {
      "name": "Baptiste Placé",
      "email": "baptiste.place@utopiaweb.fr "
    },
    {
      "name": "Joël Gaujard",
      "email": "joelm@depiltech.com",
      "homepage": "http://depiltech.com"
    }
  ],
  "keywords": [
    "function"
  ],
  "require": {
    "php": ">=5.4.0"
  },
  "autoload": {
    "files": ["date-format-conversion.php"]
  }
}

date-format-conversion.php

<?php

/**
 * Convert date/time format between `date()` and `strftime()`
 *
 * Timezone conversion is done for Unix. Windows users must exchange %z and %Z.
 *
 * Unsupported date formats : S, n, t, L, B, G, u, e, I, P, Z, c, r
 * Unsupported strftime formats : %U, %W, %C, %g, %r, %R, %T, %X, %c, %D, %F, %x
 *
 * @example Convert `%A, %B %e, %Y, %l:%M %P` to `l, F j, Y, g:i a`, and vice versa for "Saturday, March 10, 2001, 5:16 pm"
 * @link http://php.net/manual/en/function.strftime.php#96424
 *
 * @param string $format The format to parse.
 * @param string $syntax The format's syntax. Either 'strf' for `strtime()` or 'date' for `date()`.
 * @return bool|string Returns a string formatted according $syntax using the given $format or `false`.
 */
function date_format_to( $format, $syntax )
{
	// http://php.net/manual/en/function.strftime.php
	$strf_syntax = [
		// Day - no strf eq : S (created one called %O)
		'%O', '%d', '%a', '%e', '%A', '%u', '%w', '%j',
		// Week - no date eq : %U, %W
		'%V',
		// Month - no strf eq : n, t
		'%B', '%m', '%b', '%-m',
		// Year - no strf eq : L; no date eq : %C, %g
		'%G', '%Y', '%y',
		// Time - no strf eq : B, G, u; no date eq : %r, %R, %T, %X
		'%P', '%p', '%l', '%I', '%H', '%M', '%S',
		// Timezone - no strf eq : e, I, P, Z
		'%z', '%Z',
		// Full Date / Time - no strf eq : c, r; no date eq : %c, %D, %F, %x
		'%s'
	];

	// http://php.net/manual/en/function.date.php
	$date_syntax = [
		'S', 'd', 'D', 'j', 'l', 'N', 'w', 'z',
		'W',
		'F', 'm', 'M', 'n',
		'o', 'Y', 'y',
		'a', 'A', 'g', 'h', 'H', 'i', 's',
		'O', 'T',
		'U'
	];

	switch ( $syntax ) {
		case 'date':
			$from = $strf_syntax;
			$to   = $date_syntax;
			break;

		case 'strf':
			$from = $date_syntax;
			$to   = $strf_syntax;
			break;

		default:
			return false;
	}

	$pattern = array_map(
		function ( $s ) {
			return '/(?<!\\\\|\%)' . $s . '/';
		},
		$from
	);

	return preg_replace( $pattern, $to, $format );
}

/**
 * Equivalent to `date_format_to( $format, 'date' )`
 *
 * @param string $strf_format A `strftime()` date/time format
 * @return string
 */
function strftime_format_to_date_format( $strf_format )
{
	return date_format_to( $strf_format, 'date' );
}

/**
 * Equivalent to `convert_datetime_format_to( $format, 'strf' )`
 *
 * @param string $date_format A `date()` date/time format
 * @return string
 */
function date_format_to_strftime_format( $date_format )
{
	return date_format_to( $date_format, 'strf' );
}