<?php

    #
    # RFC(2)822 Email Parser
    #
    # By Cal Henderson <cal@iamcal.com>
    # This code is licensed under a Creative Commons Attribution-ShareAlike 2.5 License
    # http://creativecommons.org/licenses/by-sa/2.5/
    #
    # $Revision: 2722 $
    #

    ##################################################################################

    function is_rfc2822_valid_email_address($email){


        ####################################################################################
        #
        # NO-WS-CTL       =       %d1-8 /         ; US-ASCII control characters
        #                         %d11 /          ;  that do not include the
        #                         %d12 /          ;  carriage return, line feed,
        #                         %d14-31 /       ;  and white space characters
        #                         %d127
        # ALPHA          =  %x41-5A / %x61-7A   ; A-Z / a-z
        # DIGIT          =  %x30-39

        $no_ws_ctl    = "[\\x01-\\x08\\x0b\\x0c\\x0e-\\x1f\\x7f]";
        $alpha        = "[\\x41-\\x5a\\x61-\\x7a]";
        $digit        = "[\\x30-\\x39]";
        $cr        = "\\x0d";
        $lf        = "\\x0a";
        $crlf        = "(?:$cr$lf)";


        ####################################################################################
        #
        # obs-char        =       %d0-9 / %d11 /          ; %d0-127 except CR and
        #                         %d12 / %d14-127         ;  LF
        # obs-text        =       *LF *CR *(obs-char *LF *CR)
        # text            =       %d1-9 /         ; Characters excluding CR and LF
        #                         %d11 /
        #                         %d12 /
        #                         %d14-127 /
        #                         obs-text
        # obs-qp          =       "\" (%d0-127)
        # quoted-pair     =       ("\" text) / obs-qp

        $obs_char    = "[\\x00-\\x09\\x0b\\x0c\\x0e-\\x7f]";
        $obs_text    = "(?:$lf*$cr*(?:$obs_char$lf*$cr*)*)";
        $text        = "(?:[\\x01-\\x09\\x0b\\x0c\\x0e-\\x7f]|$obs_text)";
        $obs_qp        = "(?:\\x5c[\\x00-\\x7f])";
        $quoted_pair    = "(?:\\x5c$text|$obs_qp)";


        ####################################################################################
        #
        # obs-FWS         =       1*WSP *(CRLF 1*WSP)
        # FWS             =       ([*WSP CRLF] 1*WSP) /   ; Folding white space
        #                         obs-FWS
        # ctext           =       NO-WS-CTL /     ; Non white space controls
        #                         %d33-39 /       ; The rest of the US-ASCII
        #                         %d42-91 /       ;  characters not including "(",
        #                         %d93-126        ;  ")", or "\"
        # ccontent        =       ctext / quoted-pair / comment
        # comment         =       "(" *([FWS] ccontent) [FWS] ")"
        # CFWS            =       *([FWS] comment) (([FWS] comment) / FWS)

        #
        # note: we translate ccontent only partially to avoid an infinite loop
        # instead, we'll recursively strip comments before processing the input
        #

        $wsp        = "[\\x20\\x09]";
        $obs_fws    = "(?:$wsp+(?:$crlf$wsp+)*)";
        $fws        = "(?:(?:(?:$wsp*$crlf)?$wsp+)|$obs_fws)";
        $ctext        = "(?:$no_ws_ctl|[\\x21-\\x27\\x2A-\\x5b\\x5d-\\x7e])";
        $ccontent    = "(?:$ctext|$quoted_pair)";
        $comment    = "(?:\\x28(?:$fws?$ccontent)*$fws?\\x29)";
        $cfws        = "(($fws?$comment)*($fws?$comment|$fws))";
        $cfws        = "$fws*";


        ####################################################################################
        #
        # atext           =       ALPHA / DIGIT / ; Any character except controls,
        #                         "!" / "#" /     ;  SP, and specials.
        #                         "$" / "%" /     ;  Used for atoms
        #                         "&" / "'" /
        #                         "*" / "+" /
        #                         "-" / "/" /
        #                         "=" / "?" /
        #                         "^" / "_" /
        #                         "`" / "{" /
        #                         "|" / "}" /
        #                         "~"
        # atom            =       [CFWS] 1*atext [CFWS]

        $atext        = "($alpha|$digit|[\\x21\\x23-\\x27\\x2a\\x2b\\x2d\\x2f\\x3d\\x3f\\x5e\\x5f\\x60\\x7b-\\x7e])";
        $atom        = "($cfws?$atext+$cfws?)";


        ####################################################################################
        #
        # qtext           =       NO-WS-CTL /     ; Non white space controls
        #                         %d33 /          ; The rest of the US-ASCII
        #                         %d35-91 /       ;  characters not including "\"
        #                         %d93-126        ;  or the quote character
        # qcontent        =       qtext / quoted-pair
        # quoted-string   =       [CFWS]
        #                         DQUOTE *([FWS] qcontent) [FWS] DQUOTE
        #                         [CFWS]
        # word            =       atom / quoted-string

        $qtext        = "($no_ws_ctl|[\\x21\\x23-\\x5b\\x5d-\\x7e])";
        $qcontent    = "($qtext|$quoted_pair)";
        $quoted_string    = "($cfws?\\x22($fws?$qcontent)*$fws?\\x22$cfws?)";
        $word        = "($atom|$quoted_string)";


        ####################################################################################
        #
        # obs-local-part  =       word *("." word)
        # obs-domain      =       atom *("." atom)

        $obs_local_part    = "($word(\\x2e$word)*)";
        $obs_domain    = "($atom(\\x2e$atom)*)";


        ####################################################################################
        #
        # dot-atom-text   =       1*atext *("." 1*atext)
        # dot-atom        =       [CFWS] dot-atom-text [CFWS]

        $dot_atom_text    = "($atext+(\\x2e$atext+)*)";
        $dot_atom    = "($cfws?$dot_atom_text$cfws?)";


        ####################################################################################
        #
        # domain-literal  =       [CFWS] "[" *([FWS] dcontent) [FWS] "]" [CFWS]
        # dcontent        =       dtext / quoted-pair
        # dtext           =       NO-WS-CTL /     ; Non white space controls
        # 
        #                         %d33-90 /       ; The rest of the US-ASCII
        #                         %d94-126        ;  characters not including "[",
        #                                         ;  "]", or "\"

        $dtext        = "($no_ws_ctl|[\\x21-\\x5a\\x5e-\\x7e])";
        $dcontent    = "($dtext|$quoted_pair)";
        $domain_literal    = "($cfws?\\x5b($fws?$dcontent)*$fws?\\x5d$cfws?)";


        ####################################################################################
        #
        # local-part      =       dot-atom / quoted-string / obs-local-part
        # domain          =       dot-atom / domain-literal / obs-domain
        # addr-spec       =       local-part "@" domain

        $local_part    = "($dot_atom|$quoted_string|$obs_local_part)";
        $domain        = "($dot_atom|$domain_literal|$obs_domain)";
        $addr_spec    = "($local_part\\x40$domain)";


        #
        # we need to strip comments first (repeat until we can't find any more)
        #

        $done = 0;

        while(!$done){
            $new = preg_replace("!$comment!", '', $email);
            if (strlen($new) == strlen($email)){
                $done = 1;
            }
            $email = $new;
        }


        #
        # now match what's left
        #

        return preg_match("!^$addr_spec$!", $email) ? 1 : 0;
    }

    ##################################################################################
?>