CentOS8迁移至Ubuntu18.04后CodeIgniter 1.7.2空白页问题求助

Hey there, let's tackle this blank page issue with your old CodeIgniter 1.7.2 setup on Ubuntu 18.04 — I’ve dealt with similar legacy CI headaches before, so here are some targeted steps to dig up the root cause:

1. Force CodeIgniter to Log Its Own Errors #

Even if PHP’s error reporting is enabled, CI 1.7.2 has its own internal logging system that might be disabled by default. Head to application/config/config.php and update these settings:

$config['log_threshold'] = 2; // Logs errors and debug messages (adjust to 4 for more detail)
$config['log_path'] = './application/logs/'; // Ensure this path is correct

Critical note: The application/logs folder needs write permissions for Ubuntu’s web server user (www-data). Run these commands to fix that:

sudo chown www-data:www-data /path/to/your/app/application/logs
sudo chmod 755 /path/to/your/app/application/logs

This should start capturing CI-specific errors that PHP’s logs might miss.

2. Hunt for Legacy PHP Function Conflicts #

CI 1.7.2 is ancient (released in 2009), so it’s likely clashing with PHP 5.6+/7.2’s deprecated/removed functions:

• Check your custom libraries (like jempe_db or employees_library) for old mysql_* calls — you switched CI’s core driver to mysqli, but custom code might still be using outdated MySQL functions.
• Look for ereg* functions (deprecated in PHP 5.3, gone in 7.0) — replace them with preg_match if you find any.
• Temporarily disable session database storage: Set $config['sess_use_database'] = FALSE; in config.php to rule out session-related crashes.

3. Debug the Bootstrap Step-by-Step #

Blank pages usually mean a fatal error before any output is sent. Add manual debug checks to your main index.php (the CI entry point):

error_reporting(E_ALL);
ini_set('display_errors', 1);
ini_set('display_startup_errors', 1);

// Test if the script even starts
echo "Script initialized...<br>";

Then, add echo statements in application/config/autoload.php to pinpoint which library is breaking things:

$autoload['libraries'] = array();
echo "Loading jempe_form...<br>";
$autoload['libraries'][] = 'jempe_form';
echo "Loading jempe_db...<br>";
$autoload['libraries'][] = 'jempe_db';
// Repeat for each library in your original list

This will show you exactly where the script stops executing.

4. Check Apache’s Error Logs #

Don’t ignore the web server logs! For Apache on Ubuntu, they’re located at /var/log/apache2/error.log. Run this command to watch logs in real-time while you load the page:

sudo tail -f /var/log/apache2/error.log

You might find permission errors, missing files, or server-level issues that PHP isn’t reporting.

5. Fix File Permissions Across the Board #

Ubuntu’s www-data user needs read access to all CI files, and write access to specific folders (logs, cache). Run these commands to set proper permissions:

// Set ownership to the web server user
sudo chown -R www-data:www-data /path/to/your/application
// Set folders to 755, files to 644 (standard secure permissions)
find /path/to/your/application -type d -exec chmod 755 {} \;
find /path/to/your/application -type f -exec chmod 644 {} \;

Double-check custom library files (like jempe_form.php) to ensure they’re readable by www-data.

6. Test a Minimal CI Setup #

To rule out custom code issues, create a bare-bones test:

1. Rename your current application folder to application-old.
2. Copy the fresh application folder from a CI 1.7.2 archive into your project.
3. Update database.php with your credentials (using mysqli) and set log_threshold to 2.
4. Load the default welcome page. If this works, start adding back your custom libraries/configs one by one to find the culprit.

Legacy CI versions can be finicky with newer PHP environments, but methodical debugging almost always reveals the hidden error. Good luck!

内容的提问来源于stack exchange，提问作者Muhammad Salahuddin