Ubuntu 16.04.4下通过PHP重启Apache失败求助

Hey there, let’s dig into why your PHP script isn’t restarting Apache—this is a super common issue tied to system permissions, not just file access rights. Let’s break down the most likely causes and fixes:

1. The PHP runtime user lacks sudo permissions (the #1 culprit) #

PHP runs under Apache’s default user, www-data, which has almost no system-level privileges by default. Setting your script to 777 doesn’t change this—file permissions control who can read/write the script, not what system commands the user can run.

Fix steps: #

• Open the sudoers file safely (never edit it directly with a regular text editor):

  sudo visudo
  

• Add this line at the bottom to let www-data restart Apache without entering a password:

  www-data ALL=(ALL) NOPASSWD: /usr/sbin/service apache2 restart
  

• Save and exit (in nano, that’s Ctrl+O, Enter, Ctrl+X).

2. You’re not capturing error output (so you think there’s no error) #

By default, PHP’s exec() or system() functions only capture standard output (STDOUT), not error messages (STDERR). That’s why you’re seeing "no errors"—they’re just hidden.

Fix with debug code: #

Use this snippet to catch all output, including errors:

<?php
$output = [];
$return_code = 0;
// 2>&1 redirects STDERR to STDOUT so we can see errors
exec('sudo /usr/sbin/service apache2 restart 2>&1', $output, $return_code);

echo "Return Code: " . $return_code . "<br>";
echo "Full Output:<br>";
print_r($output);
?>

A return code of 0 means success; anything else is an error. The output will tell you exactly what’s wrong (e.g., "permission denied").

3. PHP’s execution functions are disabled #

Check if exec, system, or shell_exec are blocked in your php.ini config.

Fix: #

• Open the Apache-specific php.ini file:

  sudo nano /etc/php/7.0/apache2/php.ini
  

• Look for the disable_functions line. If any of the execution functions are listed, remove them.
• Save and restart Apache manually first:

  sudo service apache2 restart
  

4. AppArmor is blocking the command #

Ubuntu 16.04 uses AppArmor to restrict what processes can do. It might be preventing www-data from running sudo or service.

Test and fix: #

• Temporarily stop AppArmor to test:

  sudo systemctl stop apparmor
  

• If your script works now, you’ll need to create a custom AppArmor profile to allow the restart command (for production) or leave it disabled (only for testing environments).

5. Stop using 777 permissions—it’s useless and dangerous #

Setting your script to 777 doesn’t help with system command permissions, and it lets any user on the server modify your script. Revert it to a safe permission level instead:

sudo chmod 644 /path/to/your/script.php

Quick test to confirm permissions #

Run this command as the www-data user to simulate what PHP is doing:

sudo -u www-data sudo /usr/sbin/service apache2 restart

If you get an error here, that’s exactly what PHP is hitting—fix that first before troubleshooting the script.

内容的提问来源于stack exchange，提问作者Petey Howell