PHP date_parse_from_format( ) alternative in PHP 5.2

Question

Since date_parse_from_format( ) is available only in PHP 5.3, I need to write a function that mimics its behaviour in PHP 5.2.

Is it possible to write this function

Answer 1

First I'd like to thank @rudie for his answer and @jeremy refinement of his answer.

I needed a bit more flexible version would could deal with jQueryUI Datepicker with the TimePicker plugin. I also needed it to work with the \ backslash escape character to deal with the odd time formats users enter such as H\h i\m\i\n.

Here's my solution based on those previous answers that I implemented in my Connections Business Directory WordPress plugin.

It more closely matches the functionality of date_parse_from_format() and DateTime::createFromFormat().

Hope this helps someone!

 array( 'year', '\d{4}' ),            // Year with 4 Digits
        'y' => array( 'year', '\d{2}' ),            // Year with 2 Digits
        'm' => array( 'month', '\d{2}' ),           // Month with leading 0
        'n' => array( 'month', '\d{1,2}' ),         // Month without the leading 0
        'M' => array( 'month', '[A-Z][a-z]{2}' ),   // Month ABBR 3 letters
        'F' => array( 'month', '[A-Z][a-z]{2,8}' ), // Month Name
        'd' => array( 'day', '\d{2}' ),             // Day with leading 0
        'j' => array( 'day', '\d{1,2}' ),           // Day without leading 0
        'D' => array( 'day', '[A-Z][a-z]{2}' ),     // Day ABBR 3 Letters
        'l' => array( 'day', '[A-Z][a-z]{5,8}' ),   // Day Name
        'h' => array( 'hour', '\d{2}' ),            // Hour 12h formatted, with leading 0
        'H' => array( 'hour', '\d{2}' ),            // Hour 24h formatted, with leading 0
        'g' => array( 'hour', '\d{1,2}' ),          // Hour 12h formatted, without leading 0
        'G' => array( 'hour', '\d{1,2}' ),          // Hour 24h formatted, without leading 0
        'i' => array( 'minute', '\d{2}' ),          // Minutes with leading 0
        's' => array( 'second', '\d{2}' ),          // Seconds with leading 0
        'u' => array( 'hour', '\d{1,6}' ),          // Microseconds
        'a' => array( 'meridiem', '[ap]m' ),        // Lowercase ante meridiem and Post meridiem
        'A' => array( 'meridiem', '[AP]M' ),        // Uppercase ante meridiem and Post meridiem
    );

    /**
     * Create a regex used to parse the supplied datetime format.
     *
     * @access public
     * @since  8.6.4
     *
     * @param string $format The datetime format.
     *
     * @return string
     */
    private static function getFormatRegex( $format ) {

        $keys = self::$keys;

        // Convert format string to regex.
        $regex = '';
        $chars = str_split( $format );

        foreach ( $chars as $n => $char ) {

            $lastChar    = isset( $chars[ $n - 1 ] ) ? $chars[ $n - 1 ] : '';
            $skipCurrent = '\\' == $lastChar;

            if ( ! $skipCurrent && isset( $keys[ $char ] ) ) {

                $regex .= '(?P<' . $keys[ $char ][0] . '>' . $keys[ $char ][1] . ')';

            } elseif ( '\\' == $char || '!' == $char ) {

                /*
                 * No need to add the date format escaping character to the regex since it should not exist in the
                 * supplied datetime string. Including it would cause the preg_match to fail.
                 */
                //$regex .= $char;

            } else {

                $regex .= preg_quote( $char );
            }
        }

        return '#^' . $regex . '$#';
    }

    /**
     * PHP 5.2 does not have a version of @see date_parse_from_format(), this is a mostly PHP 5.2 compatible version.
     *
     * @link http://stackoverflow.com/a/14196482/5351316
     *
     * @access public
     * @since  8.6.4
     *
     * @param string $format The datetime format.
     * @param string $date   The datetime string to parse.
     *
     * @return array
     */
    public static function parseFromFormat( $format, $date ) {

        /** Setup the default values to be returned, matching @see date_parse_from_format() */
        $dt = array(
            'year'          => FALSE,
            'month'         => FALSE,
            'day'           => FALSE,
            'hour'          => FALSE,
            'minute'        => FALSE,
            'second'        => FALSE,
            'fraction'      => FALSE,
            'warning_count' => 0,
            'warnings'      => array(),
            'error_count'   => 0,
            'errors'        => array(),
            'is_localtime'  => FALSE,
            'zone_type'     => 0,
            'zone'          => 0,
            'is_dst'        => '',
        );

        // Now try to match it.
        if ( preg_match( self::getFormatRegex( $format ), $date, $matches ) ) {

            foreach ( $matches as $k => $v ) {

                // Remove unwanted indexes from resulting preg_match.
                if ( is_int( $k ) ) {

                    unset( $matches[ $k ] );
                }

                // Year, month, day, hour, minute, second and fraction should be coerced from string to int.
                if ( in_array( $k, array( 'year', 'month', 'day', 'hour', 'minute', 'second', 'fraction' ) )
                     && is_numeric( $v ) ) {

                    $matches[ $k ] = (int) $v;

                } elseif ( 'month' === $k ) {

                    $parsed = date_parse( $v );
                    $matches[ $k ] = (int) $parsed['month'];

                } elseif ( 'day' === $k ) {

                    $parsed = date_parse( $v );
                    $matches[ $k ] = (int) $parsed['day'];
                }
            }

        } else {

            $dt['error_count'] = 1;
            $dt['errors'][]    = 'Invalid date supplied.'; // @todo match error string from date_parse_from_format()
        }

        return wp_parse_args( $matches, $dt );
    }

    /**
     * PHP 5.2 does not have a version of @see DateTime::createFromFormat(), this is a mostly PHP 5.2 compatible version.
     *
     * @link http://bordoni.me/date_parse_from_format-php-5-2/
     *
     * @access public
     * @since  8.6.4
     *
     * @param  string $format  The datetime format.
     * @param  string $date    The datetime string to parse.
     *
     * @return false|DateTime  Instance of DateTime, false on failure.
     */
    public static function createFromFormat( $format, $date ) {

        $keys  = self::$keys;
        $pos   = strpos( $format, '!' );
        $chars = str_split( $format );

        // Setup default datetime values based on time now or Unix epoch based on if `!` if present in $format.
        if ( FALSE !== $pos ) {

            $datetime = array(
                'year'          => '1970',
                'month'         => '01',
                'day'           => '01',
                'hour'          => '00',
                'minute'        => '00',
                'second'        => '00',
                'fraction'      => '000000',
            );

        } else {

            /** @link http://stackoverflow.com/a/38334226/5351316 */
            list( $usec, $sec ) = explode( ' ', microtime() );

            $datetime = array(
                'year'          => date( 'Y', $sec ),
                'month'         => date( 'm', $sec ),
                'day'           => date( 'd', $sec ),
                'hour'          => date( 'H', $sec ),
                'minute'        => date( 'i', $sec ),
                'second'        => date( 's', $sec ),
                'fraction'      => substr( $usec, 2, 6 ),
            );
        }

        $parsed = self::parseFromFormat( $format, $date );

        foreach ( $chars as $n => $char ) {

            $lastChar    = isset( $chars[ $n - 1 ] ) ? $chars[ $n - 1 ] : '';
            $skipCurrent = '\\' == $lastChar;

            if ( ! $skipCurrent && isset( $keys[ $char ] ) ) {

                // Existing value exists in supplied parsed date.
                if ( $parsed[ $keys[ $char ][0] ] ) {

                    /*
                     * Replace default datetime interval with the parsed datetime interval only if
                     * an `!` was found within the supplied $format and its position is
                     * greater than the current $format character position.
                     */
                    if ( ! ( FALSE !== $pos && $pos > $n ) ) {

                        $datetime[ $keys[ $char ][0] ] = $parsed[ $keys[ $char ][0] ];
                    }
                }
            }
        }

        // Ensure the datetime integers are correctly padded with leading zeros.
        $datetime['month']  = str_pad( $datetime['month'], 2, '0', STR_PAD_LEFT );
        $datetime['day']    = str_pad( $datetime['day'], 2, '0', STR_PAD_LEFT );
        $datetime['hour']   = str_pad( $datetime['hour'], 2, '0', STR_PAD_LEFT );
        $datetime['minute'] = str_pad( $datetime['minute'], 2, '0', STR_PAD_LEFT );
        $datetime['second'] = str_pad( $datetime['second'], 2, '0', STR_PAD_LEFT );

        // Parse the $datetime into a string which can be parsed by DateTime().
        $formatted = strtr( 'year-month-day hour:minute:second.fraction', $datetime );

        // Sanity check to make sure the datetime is valid.
        if ( ! strtotime( $formatted ) ) {

            return FALSE;
        }

        // Return a new DateTime instance.
        return new DateTime( $formatted );
    }
}