PHP: Conversion Filters

Conversion Filters

Like the string.* filters, the convert.* filters perform actions similar to their names. For more information on a given filter, refer to the manual page for the corresponding function.

convert.base64-encode and convert.base64-decode

Use of these filters are equivalent to processing all stream data through the base64_encode() and base64_decode() functions respectively. convert.base64-encode supports parameters given as an associative array. If line-length is given, the base64 output will be split into chunks of line-length characters each. If line-break-chars is given, each chunk will be delimited by the characters given. These parameters give the same effect as using base64_encode() with chunk_split().

Example #1 convert.base64-encode & convert.base64-decode

<?php
$fp = fopen('php://output', 'w');
stream_filter_append($fp, 'convert.base64-encode');
fwrite($fp, "This is a test.\n");
fclose($fp);
/* Outputs:  VGhpcyBpcyBhIHRlc3QuCg==  */

$param = array('line-length' => 8, 'line-break-chars' => "\r\n");
$fp = fopen('php://output', 'w');
stream_filter_append($fp, 'convert.base64-encode', STREAM_FILTER_WRITE, $param);
fwrite($fp, "This is a test.\n");
fclose($fp);
/* Outputs:  VGhpcyBp
          :  cyBhIHRl
          :  c3QuCg==  */

$fp = fopen('php://output', 'w');
stream_filter_append($fp, 'convert.base64-decode');
fwrite($fp, "VGhpcyBpcyBhIHRlc3QuCg==");
fclose($fp);
/* Outputs:  This is a test.  */
?>

convert.quoted-printable-encode and convert.quoted-printable-decode

Use of the decode version of this filter is equivalent to processing all stream data through the quoted_printable_decode() function. There is no function equivalent to convert.quoted-printable-encode. convert.quoted-printable-encode supports parameters given as an associative array. In addition to the parameters supported by convert.base64-encode, convert.quoted-printable-encode also supports boolean arguments binary and force-encode-first. convert.base64-decode only supports the line-break-chars parameter as a type-hint for stripping from the encoded payload.

Example #2 convert.quoted-printable-encode & convert.quoted-printable-decode

<?php
$fp = fopen('php://output', 'w');
stream_filter_append($fp, 'convert.quoted-printable-encode');
fwrite($fp, "This is a test.\n");
/* Outputs:  =This is a test.=0A  */
?>

convert.iconv.*

The convert.iconv.* filters are available, if iconv support is enabled, and their use is equivalent to processing all stream data with iconv(). These filters do not support parameters, but instead expect the input and output encodings to be given as part of the filter name, i.e. either as convert.iconv.<input-encoding>.<output-encoding> or convert.iconv.<input-encoding>/<output-encoding> (both notations are semantically equivalent).

Example #3 convert.iconv.*

<?php
$fp = fopen('php://output', 'w');
stream_filter_append($fp, 'convert.iconv.utf-16le.utf-8');
fwrite($fp, "T\0h\0i\0s\0 \0i\0s\0 \0a\0 \0t\0e\0s\0t\0.\0\n\0");
fclose($fp);
/* Outputs: This is a test. */
?>

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User Contributed Notes 1 note

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marcus at synchromedia dot co dot uk ¶

2 years ago

It's not quite obvious what all the available parameters are for convert.quoted-printable-encode. If you want the stream filter to act the same way as the quoted_printable_encode function, you need these extra params, for example:

stream_filter_append(
    STDOUT,
    'convert.quoted-printable-encode',
    STREAM_FILTER_WRITE,
    [
        'line-break-chars' => PHP_EOL,
        'line-length' => 75,
    ]
);
echo stream_copy_to_stream(STDIN, STDOUT);

Without these extra params set, you may get no wrapping at all, or wrapping using the wrong line break sequence.

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