Why can't I run the composer script from PHP using exec, shell_exec, system?

Question

I can run about any binary but not that composer.phar using PHP's exec or shell_exec.

In the same folder I have composer and another php executable with same permissions:

ls -lh
total 1,8M
-rwxr-xr-x  1 me me 1,8M août  22 20:48 composer.phar
-rwxr-xr-x  1 me me   39 août  22 21:05 test.php

Test.php contains:

#!/usr/bin/env php
<?php
print 'hello';

I then have this script:

<?php
print $cmd  = "composer.phar --version 2>&1" ;
print "<br>";

$return  = exec( $cmd );
var_dump($return);

print "<br><br>";

print $cmd  = "test.php 2>&1";
print "<br>";

$return  = shell_exec( $cmd );
var_dump($return);

Here is what I get:

composer.phar --version 2>&1
[...]Process.php:81:string 'sh: 1: : Permission denied' (length=26)

test.php 2>&1
[...]Process.php:88:string 'hello' (length=5)

Why do I get that string 'sh: 1: : Permission denied' error? I tried executing in PHP with /usr/bin/env php composer.php /usr/bin/php composer.php, I get the same error.

Answer 1

I solved it by disabling the xdebug extension.

From the doc:

To improve performance when the xdebug extension is enabled, Composer automatically restarts PHP without it.

So I guess that this "PHP restart" is an issue when calling the binary/phar from PHP.

It is be possible to use the environment variable COMPOSER_ALLOW_XDEBUG to get it working with xdebug, also disbaling a few xdebug options that could alter performances:

<?php
$result = shell_exec('COMPOSER_ALLOW_XDEBUG=1 /usr/bin/env php -d xdebug.remote_enable=0 -d xdebug.profiler_enable=0 -d xdebug.default_enable=0 composer.phar --version 2>&1');

Answer 2

I think it will work with system('php /usr/local/bin/composer install -d /...'), because if you just run composer directly in a shell it will work by reading the shebang at the beginning of the file that says it should be executed by php, but using system() you don't have a shell so you need to specify this yourself.