postfix pipe to php script: how to fully log php errors/warning/notices?

Question

In postfix on Debian 10 I’m piping received mail to a php script – in master.cf:

mail-pipe-script unix - n n - - pipe flags=DRhu user=mail-pipe-user argv=/usr/bin/php /var/www/html/admin/mail_pipe.php

all works well but any php errors or warnings are returned to postfix and logged in truncated form to /var/log/mail.log - I’d like to view the whole error it its own log file, or at least in mail.log without truncation. The closest I’ve got is at the top of mail_pipe.php:

#!/usr/bin/php
<?php
$x= exec('command 2>>  /var/log/mail.log');

But permissions are denied and of course fatal errors won’t get logged. I‘m a bit jumpy about lowering log permissions. I’ve also tried other log destinations. mail_pipe.php is owned as mail-pipe-user:www-data BTW mail_pipe.php reads the email using stdin:

$fd = fopen("php://stdin", "r");

Can someone advise a better way forward for fully logging the php scripts errors and warnings etc?

Thanks!

Answer 1

AFAIK PHP standard I/O streams cannot be redefined, only closed. If you have access to script source code, you could define an error handler via set_error_handler. If not there's an option to wrap your script with another, that will take control over targets I/O streams.

<?php
// Call me wrapper.php

$pipes = [];
$real_process = proc_open(
    'php ./wrapped.php',
    [
        ["pipe", "r"],
        ["pipe", "w"],
        ["pipe", "w"]
    ],
    $pipes
);

if( is_resource($real_process) ){
    
    // Passing my stdin as-is
    fwrite($pipes[0], stream_get_contents(STDIN));
    fclose($pipes[0]);

    $real_process_said = stream_get_contents($pipes[1]);
    fclose($pipes[1]);

    $real_process_whined = stream_get_contents($pipes[2]);
    fclose($pipes[2]);

    proc_close($real_process);

    print "STDOUT was: $real_process_said";
    print "STDERR was: $real_process_whined";

}

<?php
// Call me wrapped.php

print "The STDIN is: " . stream_get_contents(STDIN);

fwrite(STDERR, "i'm wrapped pleas halp!");