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

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)

Answer 1

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);

Answer 2

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.

Answer 3

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);
}

Answer 4

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.