How can I check if stdin exists in PHP ( php-cgi )?

Question

Setup and Background

I am working on script that needs to run as /usr/bin/php-cgi instead /usr/local/bin/php and I'm having trouble checking for stdin

If I use /usr/local/bin/php as the interpreter I can do something like

if defined('STDIN'){ ... }

This doesn't seem to work with php-cgi - Looks to always be undefined. I checked the man page for php-cgi but didn't find it very helpful. Also, if I understand it correctly, the STDIN constant is a file handle for php://stdin. I read somewhere that constant is not supposed to be available in php-cgi

Requirements

The shebang needs to be #!/usr/bin/php-cgi -q
The script will sometimes be passed arguments
The script will sometimes receive input via STDIN

Current Script

#!/usr/bin/php-cgi -q
<?php

$stdin = '';
$fh = fopen('php://stdin', 'r');

if($fh)
{

    while ($line = fgets( $fh )) {
            $stdin .= $line;
    }
    fclose($fh);

}

echo $stdin;

Problematic Behavior

This works OK:

$ echo hello | ./myscript.php 
hello

This just hangs:

./myscript.php

These things don't work for me:

Checking defined('STDIN') // always returns false
Looking to see if CONTENT_LENGTH is defined
Checking variables and constants

I have added this to the script and run it both ways:

print_r(get_defined_constants());
print_r($GLOBALS);
print_r($_COOKIE);
print_r($_ENV);
print_r($_FILES);
print_r($_GET);
print_r($_POST);
print_r($_REQUEST);
print_r($_SERVER);
echo shell_exec('printenv');

I then diff'ed the output and it is the same.

I don't know any other way to check for / get stdin via php-cgi without locking up the script if it does not exist.

/usr/bin/php-cgi -v yields: PHP 5.4.17 (cgi-fcgi)

Pavel Kurinnoy · Accepted Answer · 2016-04-08 07:54:23Z

7

You can use the select function such as:

$stdin = '';
$fh = fopen('php://stdin', 'r');
$read  = array($fh);
$write = NULL;
$except = NULL;
if ( stream_select( $read, $write, $except, 0 ) === 1 ) {
    while ($line = fgets( $fh )) {
            $stdin .= $line;
    }
}
fclose($fh);

answered Apr 8, 2016 at 7:54

Pavel Kurinnoy

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1 Comment

YAMM Over a year ago

perfect solution! covers all my requirements

Community · Accepted Answer · 2017-05-23 11:46:40Z

3

Regarding your specific problem of hanging when there is no input: php stream reads are blocking operations by default. You can change that behavior with stream_set_blocking(). Like so:

$fh = fopen('php://stdin', 'r');
stream_set_blocking($fh, false);
$stdin = fgets($fh);
echo "stdin: '$stdin'";  // immediately returns "stdin: ''"

Note that this solution does not work with that magic file handle STDIN.

edited May 23, 2017 at 11:46

CommunityBot

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answered Jun 9, 2015 at 19:04

Seth Battin

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Comments

Yaro · Accepted Answer · 2020-05-13 11:25:57Z

2

stream_get_meta_data helped me :)

And as mentioned in the previous answer by Seth Battin stream_set_blocking($fh, false); works very well 👍

The next code reads data from the command line if provided and skips when it's not.

For example: echo "x" | php render.php and php render.php

In the first case, I provide some data from another stream (I really need to see the changed files from git, something like git status | php render.php.

Here is an example of my solution which works:

$input = [];

$fp = fopen('php://stdin', 'r+');
$info = stream_get_meta_data($fp);

if (!$info['seekable'] && $fp) {
    while (false !== ($line = fgets($fp))) {
        $input[] = trim($line);
    }
    fclose($fp);
}

edited May 13, 2020 at 11:25

answered May 13, 2020 at 11:16

Yaro

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1 Comment

user3342816 Over a year ago

Note that this does not work with redirects. I.e. $ ./foo.php< data-file.txt

Cyclonecode · Accepted Answer · 2013-08-09 00:44:23Z

0

The problem is that you create a endless loop with the while($line = fgets($fh)) part in your code.

$stdin = '';
$fh = fopen('php://stdin','r');
if($fh) {
  // read *one* line from stdin upto "\r\n"
  $stdin = fgets($fh);
  fclose($fh);
}
echo $stdin;

The above would work if you're passing arguments like echo foo=bar | ./myscript.php and will read a single line when you call it like ./myscript.php If you like to read more lines and keep your original code you can send a quit signal CTRL + D

To get parameters passed like ./myscript.php foo=bar you could check the contents of the $argv variable, in which the first argument always is the name of the executing script:

 ./myscript.php foo=bar

 // File: myscript.php
 $stdin = '';
 for($i = 1; $i < count($argv); i++) {
    $stdin .= $argv[$i];
 }

I'm not sure that this solves anything but perhaps it give you some ideas.

edited Aug 9, 2013 at 0:44

answered Aug 8, 2013 at 23:58

Cyclonecode

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3 Comments

cwd Over a year ago

thanks but i don't think that this is the problem - I tried putting an echo statement in my while loop before posting the question and it did not continuously spit out output - I really do believe it is "hanging" trying to read stdin

Cyclonecode Over a year ago

Strange if I echo in the while loop I see different content each time I press enter? So if you write something and press enter and then do a ctrl + d you don't get the output echoed at all?

Cyclonecode Over a year ago

@cwd - If you call the script without any input i.e ./myscript.php then it would stop at the fgets(...) until you press enter, isn't this the reason why you don't get any output if you add a echo inside your loop?

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