PHP で exec 関数を使ってブラウザから呼び出した命令を実行できない時の対処法

exec("hoge 2>&1",$dum,$rtn); // 2>&1 で標準エラー出力も標準出力へ吐き出す
echo('<pre>'); // フォーマットを整える
var_dump($dum); // 標準出力 (標準エラー出力を含む) をブラウザに出力
echo('<pre>');
echo("return: $rtn"); // hoge 命令の返り値を "return: 返り値" の形で出力

array(1) {
  [0]=>
  string(23) "sh: 1: hoge: not found"
}
return: 127

$ hoge

$ sudo find / -type f -name "hoge"

$ export PATH=$PATH:/path/to/bin

$ echo 'export PATH="$PATH:/path/to/bin"' >> ~/.bashrc

echo(getenv("PATH"));

/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

echo(getenv("PATH"));
echo('<br>');
$PATH = getenv("PATH");
putenv("PATH=$PATH:/path/to/bin");
echo(getenv("PATH"));

/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/path/to/bin

array(0) {
}
return: 0

exec("python /path/to/hoge.py 2>&1",$dum,$rtn);

array(4) {
  [0]=>
  string(34) "Traceback (most recent call last):"
  [1]=>
  string(70) "  File "/path/to/hoge.py", line 13, in "
  [2]=>
  string(34) "    import selenium"
  [3]=>
  string(47) "ModuleNotFoundError: No module named 'selenium'"
}
return: 1

exec("which python",$dum,$rtn);

array(1) {
  [0]=>
  string(16) "/usr/bin/python"
}
return: 0

exec("/usr/bin/python /path/to/hoge.py 2>&1",$dum,$rtn);

$ sudo pip install selenium

$ python
Python 3.7.3 (default, Jan 22 2021, 20:04:44)
[GCC 8.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import selenium
>>> print(selenium.__path__)
['/path/to/home/.local/lib/python3.7/site-packages/selenium']
>>> import sys
>>> print(sys.path)
['', '/usr/lib/python37.zip', '/usr/lib/python3.7', '/usr/lib/python3.7/lib-dynload', '/path/to/home/.local/lib/python3.7/site-packages', '/usr/local/lib/python3.7/dist-packages', '/usr/lib/python3/dist-packages']
>>> exit()

import sys
print(sys.path)
import selenium

exec("/usr/bin/python /path/to/path_test.py 2>&1",$dum,$rtn);

array(1) {
  [0]=>
  string(169) "['/path/to/home', '/usr/lib/python37.zip', '/usr/lib/python3.7', '/usr/lib/python3.7/lib-dynload', '/usr/local/lib/python3.7/dist-packages', '/usr/lib/python3/dist-packages']"
  [1]=>
  string(34) "Traceback (most recent call last):"
  [2]=>
  string(51) "  File "/path/to/path_test.py", line 3, in "
  [3]=>
  string(19) "    import selenium"
  [4]=>
  string(47) "ModuleNotFoundError: No module named 'selenium'"
}
return: 0

import sys
# パスを追加
sys.path.append("/path/to/home/.local/lib/python3.7/site-packages")
print(sys.path)
import selenium

array(5) {
  [0]=>
  string(216) "['/path/to/home', '/usr/lib/python37.zip', '/usr/lib/python3.7', '/usr/lib/python3.7/lib-dynload', '/usr/local/lib/python3.7/dist-packages', '/usr/lib/python3/dist-packages', '/path/to/home/.local/lib/python3.7/site-packages']"
  [1]=>
  string(34) "Traceback (most recent call last):"
  [2]=>
  string(52) "  File "/path/to/path_test.py", line 10, in "
  [3]=>
  string(19) "    import selenium"
  [4]=>
  string(47) "ModuleNotFoundError: No module named 'selenium'"
}
return: 1

$ cd /path/to/home
$ ls -la
drwx------  5 user user  4096 Jul  2  2020 .local

$ chmod -R 744 .local # これは少し危険です

$ cp -r /path/to/home/.local/lib/python3.7/site-packages/selenium /path/to/home
$ chmod -R 744 selenium

import sys
print(sys.path)
import selenium

array(1) {
  [0]=>
  string(216) "['/path/to/home', '/usr/lib/python37.zip', '/usr/lib/python3.7', '/usr/lib/python3.7/lib-dynload', '/usr/local/lib/python3.7/dist-packages', '/usr/lib/python3/dist-packages']"
}
return: 0