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

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);

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.

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.phpand 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);}