php - Converting named HTML entities to numeric HTML entities

Question

Is there a PHP function to convert named HTML entities into their respective numeric HTML entities?

For example:

$str = "Oggi è un bel giorno";
echo entities_to_unicode($str); // Oggi è un bel giorno

Thanks in advance, have a nice day!

Answer 1

You are looking for a simple translation function from named HTML entities to their numeric counterpart.

This can be done by using a translation table (that is an array) and the string translation function (strtr):

$translated = strtr($string, $HTML401NamedToNumeric);

This works for $string being UTF-8 encoded or of a single-byte character set.

Example array for the HTML 4.01 named entities as specified by W3C as used above follows. It contains 252 entities. If you want to support XHTML, then there is one more (I put it at the end):

$HTML401NamedToNumeric = array(
    ' '     => ' ',  # no-break space = non-breaking space, U+00A0 ISOnum
    '¡'    => '¡',  # inverted exclamation mark, U+00A1 ISOnum
    '¢'     => '¢',  # cent sign, U+00A2 ISOnum
    '£'    => '£',  # pound sign, U+00A3 ISOnum
    '¤'   => '¤',  # currency sign, U+00A4 ISOnum
    '¥'      => '¥',  # yen sign = yuan sign, U+00A5 ISOnum
    '¦'   => '¦',  # broken bar = broken vertical bar, U+00A6 ISOnum
    '§'     => '§',  # section sign, U+00A7 ISOnum
    '¨'      => '¨',  # diaeresis = spacing diaeresis, U+00A8 ISOdia
    '©'     => '©',  # copyright sign, U+00A9 ISOnum
    'ª'     => 'ª',  # feminine ordinal indicator, U+00AA ISOnum
    '«'    => '«',  # left-pointing double angle quotation mark = left pointing guillemet, U+00AB ISOnum
    '¬'      => '¬',  # not sign, U+00AC ISOnum
    '­'      => '­',  # soft hyphen = discretionary hyphen, U+00AD ISOnum
    '®'      => '®',  # registered sign = registered trade mark sign, U+00AE ISOnum
    '¯'     => '¯',  # macron = spacing macron = overline = APL overbar, U+00AF ISOdia
    '°'      => '°',  # degree sign, U+00B0 ISOnum
    '±'   => '±',  # plus-minus sign = plus-or-minus sign, U+00B1 ISOnum
    '²'     => '²',  # superscript two = superscript digit two = squared, U+00B2 ISOnum
    '³'     => '³',  # superscript three = superscript digit three = cubed, U+00B3 ISOnum
    '´'    => '´',  # acute accent = spacing acute, U+00B4 ISOdia
    'µ'    => 'µ',  # micro sign, U+00B5 ISOnum
    '¶'     => '¶',  # pilcrow sign = paragraph sign, U+00B6 ISOnum
    '·'   => '·',  # middle dot = Georgian comma = Greek middle dot, U+00B7 ISOnum
    '¸'    => '¸',  # cedilla = spacing cedilla, U+00B8 ISOdia
    '¹'     => '¹',  # superscript one = superscript digit one, U+00B9 ISOnum
    'º'     => 'º',  # masculine ordinal indicator, U+00BA ISOnum
    '»'    => '»',  # right-pointing double angle quotation mark = right pointing guillemet, U+00BB ISOnum
    '¼'   => '¼',  # vulgar fraction one quarter = fraction one quarter, U+00BC ISOnum
    '½'   => '½',  # vulgar fraction one half = fraction one half, U+00BD ISOnum
    '¾'   => '¾',  # vulgar fraction three quarters = fraction three quarters, U+00BE ISOnum
    '¿'   => '¿',  # inverted question mark = turned question mark, U+00BF ISOnum
    'À'   => 'À',  # latin capital letter A with grave = latin capital letter A grave, U+00C0 ISOlat1
    'Á'   => 'Á',  # latin capital letter A with acute, U+00C1 ISOlat1
    'Â'    => 'Â',  # latin capital letter A with circumflex, U+00C2 ISOlat1
    'Ã'   => 'Ã',  # latin capital letter A with tilde, U+00C3 ISOlat1
    'Ä'     => 'Ä',  # latin capital letter A with diaeresis, U+00C4 ISOlat1
    'Å'    => 'Å',  # latin capital letter A with ring above = latin capital letter A ring, U+00C5 ISOlat1
    'Æ'    => 'Æ',  # latin capital letter AE = latin capital ligature AE, U+00C6 ISOlat1
    'Ç'   => 'Ç',  # latin capital letter C with cedilla, U+00C7 ISOlat1
    'È'   => 'È',  # latin capital letter E with grave, U+00C8 ISOlat1
    'É'   => 'É',  # latin capital letter E with acute, U+00C9 ISOlat1
    'Ê'    => 'Ê',  # latin capital letter E with circumflex, U+00CA ISOlat1
    'Ë'     => 'Ë',  # latin capital letter E with diaeresis, U+00CB ISOlat1
    'Ì'   => 'Ì',  # latin capital letter I with grave, U+00CC ISOlat1
    'Í'   => 'Í',  # latin capital letter I with acute, U+00CD ISOlat1
    'Î'    => 'Î',  # latin capital letter I with circumflex, U+00CE ISOlat1
    'Ï'     => 'Ï',  # latin capital letter I with diaeresis, U+00CF ISOlat1
    'Ð'      => 'Ð',  # latin capital letter ETH, U+00D0 ISOlat1
    'Ñ'   => 'Ñ',  # latin capital letter N with tilde, U+00D1 ISOlat1
    'Ò'   => 'Ò',  # latin capital letter O with grave, U+00D2 ISOlat1
    'Ó'   => 'Ó',  # latin capital letter O with acute, U+00D3 ISOlat1
    'Ô'    => 'Ô',  # latin capital letter O with circumflex, U+00D4 ISOlat1
    'Õ'   => 'Õ',  # latin capital letter O with tilde, U+00D5 ISOlat1
    'Ö'     => 'Ö',  # latin capital letter O with diaeresis, U+00D6 ISOlat1
    '×'    => '×',  # multiplication sign, U+00D7 ISOnum
    'Ø'   => 'Ø',  # latin capital letter O with stroke = latin capital letter O slash, U+00D8 ISOlat1
    'Ù'   => 'Ù',  # latin capital letter U with grave, U+00D9 ISOlat1
    'Ú'   => 'Ú',  # latin capital letter U with acute, U+00DA ISOlat1
    'Û'    => 'Û',  # latin capital letter U with circumflex, U+00DB ISOlat1
    'Ü'     => 'Ü',  # latin capital letter U with diaeresis, U+00DC ISOlat1
    'Ý'   => 'Ý',  # latin capital letter Y with acute, U+00DD ISOlat1
    'Þ'    => 'Þ',  # latin capital letter THORN, U+00DE ISOlat1
    'ß'    => 'ß',  # latin small letter sharp s = ess-zed, U+00DF ISOlat1
    'à'   => 'à',  # latin small letter a with grave = latin small letter a grave, U+00E0 ISOlat1
    'á'   => 'á',  # latin small letter a with acute, U+00E1 ISOlat1
    'â'    => 'â',  # latin small letter a with circumflex, U+00E2 ISOlat1
    'ã'   => 'ã',  # latin small letter a with tilde, U+00E3 ISOlat1
    'ä'     => 'ä',  # latin small letter a with diaeresis, U+00E4 ISOlat1
    'å'    => 'å',  # latin small letter a with ring above = latin small letter a ring, U+00E5 ISOlat1
    'æ'    => 'æ',  # latin small letter ae = latin small ligature ae, U+00E6 ISOlat1
    'ç'   => 'ç',  # latin small letter c with cedilla, U+00E7 ISOlat1
    'è'   => 'è',  # latin small letter e with grave, U+00E8 ISOlat1
    'é'   => 'é',  # latin small letter e with acute, U+00E9 ISOlat1
    'ê'    => 'ê',  # latin small letter e with circumflex, U+00EA ISOlat1
    'ë'     => 'ë',  # latin small letter e with diaeresis, U+00EB ISOlat1
    'ì'   => 'ì',  # latin small letter i with grave, U+00EC ISOlat1
    'í'   => 'í',  # latin small letter i with acute, U+00ED ISOlat1
    'î'    => 'î',  # latin small letter i with circumflex, U+00EE ISOlat1
    'ï'     => 'ï',  # latin small letter i with diaeresis, U+00EF ISOlat1
    'ð'      => 'ð',  # latin small letter eth, U+00F0 ISOlat1
    'ñ'   => 'ñ',  # latin small letter n with tilde, U+00F1 ISOlat1
    'ò'   => 'ò',  # latin small letter o with grave, U+00F2 ISOlat1
    'ó'   => 'ó',  # latin small letter o with acute, U+00F3 ISOlat1
    'ô'    => 'ô',  # latin small letter o with circumflex, U+00F4 ISOlat1
    'õ'   => 'õ',  # latin small letter o with tilde, U+00F5 ISOlat1
    'ö'     => 'ö',  # latin small letter o with diaeresis, U+00F6 ISOlat1
    '÷'   => '÷',  # division sign, U+00F7 ISOnum
    'ø'   => 'ø',  # latin small letter o with stroke, = latin small letter o slash, U+00F8 ISOlat1
    'ù'   => 'ù',  # latin small letter u with grave, U+00F9 ISOlat1
    'ú'   => 'ú',  # latin small letter u with acute, U+00FA ISOlat1
    'û'    => 'û',  # latin small letter u with circumflex, U+00FB ISOlat1
    'ü'     => 'ü',  # latin small letter u with diaeresis, U+00FC ISOlat1
    'ý'   => 'ý',  # latin small letter y with acute, U+00FD ISOlat1
    'þ'    => 'þ',  # latin small letter thorn, U+00FE ISOlat1
    'ÿ'     => 'ÿ',  # latin small letter y with diaeresis, U+00FF ISOlat1
    'ƒ'     => 'ƒ',  # latin small f with hook = function = florin, U+0192 ISOtech
    'Α'    => 'Α',  # greek capital letter alpha, U+0391
    'Β'     => 'Β',  # greek capital letter beta, U+0392
    'Γ'    => 'Γ',  # greek capital letter gamma, U+0393 ISOgrk3
    'Δ'    => 'Δ',  # greek capital letter delta, U+0394 ISOgrk3
    'Ε'  => 'Ε',  # greek capital letter epsilon, U+0395
    'Ζ'     => 'Ζ',  # greek capital letter zeta, U+0396
    'Η'      => 'Η',  # greek capital letter eta, U+0397
    'Θ'    => 'Θ',  # greek capital letter theta, U+0398 ISOgrk3
    'Ι'     => 'Ι',  # greek capital letter iota, U+0399
    'Κ'    => 'Κ',  # greek capital letter kappa, U+039A
    'Λ'   => 'Λ',  # greek capital letter lambda, U+039B ISOgrk3
    'Μ'       => 'Μ',  # greek capital letter mu, U+039C
    'Ν'       => 'Ν',  # greek capital letter nu, U+039D
    'Ξ'       => 'Ξ',  # greek capital letter xi, U+039E ISOgrk3
    'Ο'  => 'Ο',  # greek capital letter omicron, U+039F
    'Π'       => 'Π',  # greek capital letter pi, U+03A0 ISOgrk3
    'Ρ'      => 'Ρ',  # greek capital letter rho, U+03A1
    'Σ'    => 'Σ',  # greek capital letter sigma, U+03A3 ISOgrk3
    'Τ'      => 'Τ',  # greek capital letter tau, U+03A4
    'Υ'  => 'Υ',  # greek capital letter upsilon, U+03A5 ISOgrk3
    'Φ'      => 'Φ',  # greek capital letter phi, U+03A6 ISOgrk3
    'Χ'      => 'Χ',  # greek capital letter chi, U+03A7
    'Ψ'      => 'Ψ',  # greek capital letter psi, U+03A8 ISO