UtfNormalUtil.php

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<?php
function codepointToUtf8( $codepoint ) {
    if($codepoint <     0x80) return chr($codepoint);
    if($codepoint <    0x800) return chr($codepoint >>  6 & 0x3f | 0xc0) .
                                     chr($codepoint       & 0x3f | 0x80);
    if($codepoint <  0x10000) return chr($codepoint >> 12 & 0x0f | 0xe0) .
                                     chr($codepoint >>  6 & 0x3f | 0x80) .
                                     chr($codepoint       & 0x3f | 0x80);
    if($codepoint < 0x110000) return chr($codepoint >> 18 & 0x07 | 0xf0) .
                                     chr($codepoint >> 12 & 0x3f | 0x80) .
                                     chr($codepoint >>  6 & 0x3f | 0x80) .
                                     chr($codepoint       & 0x3f | 0x80);

    echo "Asked for code outside of range ($codepoint)\n";
    die( -1 );
}

function hexSequenceToUtf8( $sequence ) {
    $utf = '';
    foreach( explode( ' ', $sequence ) as $hex ) {
        $n = hexdec( $hex );
        $utf .= codepointToUtf8( $n );
    }
    return $utf;
}

function utf8ToHexSequence( $str ) {
    $buf = '';
    foreach ( preg_split( '//u', $str, -1, PREG_SPLIT_NO_EMPTY ) as $cp ) {
        $buf .= sprintf( '%04x ', utf8ToCodepoint( $cp ) );
    }
    return rtrim( $buf );
}

function utf8ToCodepoint( $char ) {
    # Find the length
    $z = ord( $char[0] );
    if ( $z & 0x80 ) {
        $length = 0;
        while ( $z & 0x80 ) {
            $length++;
            $z <<= 1;
        }
    } else {
        $length = 1;
    }

    if ( $length != strlen( $char ) ) {
        return false;
    }
    if ( $length == 1 ) {
        return ord( $char );
    }

    # Mask off the length-determining bits and shift back to the original location
    $z &= 0xff;
    $z >>= $length;

    # Add in the free bits from subsequent bytes
    for ( $i=1; $i < $length; $i++ ) {
        $z <<= 6;
        $z |= ord( $char[$i] ) & 0x3f;
    }

    return $z;
}

function escapeSingleString( $string ) {
    return strtr( $string,
        array(
            '\\' => '\\\\',
            '\'' => '\\\''
        ));
}