Why does PHP throw “Segmentation fault (11)” after “mysql_connect”, or upon “mysql_close”?

Question

I have Ubuntu-9.04 and am using XAMPP-1.7.2 to develop a web application. The problem is that when I try to view a PHP file I wrote by visiting localhost/folder/file.php, Firefox offers me to download it instead of showing me the file as a web page. If I do download it and open it in my favorite text editor, I get an empty file with nothing in it...

UPDATE: Works on another server Well, I uploaded the page to another server, and I can see it fine! So the problem is not with Firefox. Nor is it with the code itself. My server or its configuration must be the problem. Does that give any of you a clue as to what's happening?

UPDATE: Isolating the problem Firefox offers to download only the first of these three files:

test1.php is offered as a download

<?php
    mysql_connect("localhost","root","");
    mysql_close();
?>

test2.php outputs: Warning: mysql_close(): no MySQL-Link resource supplied in /opt/lampp/htdocs/test.php on line 3

<?php
    //mysql_connect("localhost","root","");
    mysql_close();
?>

test3.php outputs a blank page

<?php
    mysql_connect("localhost","root","");
    //mysql_close();
?>

I know that my server is up and running and it tells me that PHP5 is on, and running as well.

Here is what I get in the XAMPP error log when the problem occurs (truncated and formatted for clarity):

[notice] child pid 7338 exit signal Segmentation fault (11)

Oh, and firefox can see the file without a problem on my other computer (windows XP SP3 and easyPHP as server) Does anyone know what I can do to solve this problem?

UPDATE: using error_log()

Here is my try at using error_log(): test4.php

<?php
    error_log("Start of file reached by PHP");
    mysql_connect("localhost","root","");
    error_log("mysql_connect executed");
    mysql_close();
    error_log("mysql_close executed");
?>

This is what it produces in the XAMPP error log (trucated for clarity):

[error] [client 127.0.0.1] Start of file reached by PHP
[error] [client 127.0.0.1] mysql_connect executed
[notice] child pid 5338 exit signal Segmentation fault (11)

Answer 1

Smells like your mysql install. Is mysql running as a service? Does your root account really have no password? What mysql extensions are loaded in php.ini? There's a php_mssql.dll which can easily be mistaken for php_msql.dll, but I'm fairly certain the php_mssql.dll is for windows only.

Have you edited your php.ini /opt/lampp/php/php.ini? These may help with debugging:

error_reporting  =  E_ALL & ~E_NOTICE
display_errors = On
display_startup_errors = On ;but you'll want to turn this off soon ;)
mysql.trace_mode = On

Also worth looking at, the port number used. Is $MYSQL_TCP_PORT set? How about the mysql-tcp entry in /etc/services?

Update: Have you tried checking the return value of the connect function? I'm wondering if you example is too minimal. Try making your test look like this:

<?php

$db = mysql_connect("localhost","root","myrootpassword");
if (!$db) {
    die('Could not connect: ' . mysql_error());
}
else {
    $result = mysql_query("show databases");
   print "
   <h1>Test executed from ". $_SERVER['SCRIPT_NAME']. "</h1>

    \n";
    print "Script name: ". $_SERVER['SCRIPT_FILENAME'] ." <hr>\n";
    while ($line = mysql_fetch_array($result))
    {
        print "$line[0]<br>\n";
    }
}       
mysql_close($db);

?>

This example ensure you send something back that looks like HTML whether your script fails or not. I was able to reproduce your symptoms with no root password set, so it's apparently not only good practice, but it's required to be non-empty.

I was able to turn your problem into a a solution by

1. Setting the root password
2. returning something from the script on connect

Instead of passing in "" as the root password, if it really is nothing, try using mysql.default_password as the password. The default value for mysql.default_password is NULL.

Answer 2

This could be a hardware problem or an Apache/PHP configuration problem. I've usually seen Signal 11 with memory problems. Look at your configs to make sure that the PHP memory limit isn't higher than the Apache memory limit or similar.

It sounds like your php_mod is crashing mid-program, so Apache is just tossing the php file at you with a non-html content-type header, which makes your browser treat it as a download. That's just a guess, though. You need to gather some more information.

Add some error_log() calls to your PHP program so that you can isolate when the crash actually occurs in your code. If that doesn't help narrow it down, set up Apache to create a core dump and use gdb to figure out where the segfault starts. My bet is mod_php.so.

Answer 3

You say it's all up and running and that simple files are showing up okay. But then some files are prompting you to save the PHP file. This means you'll have to look at the code of those pages where it's breaking and asking you to save.

It's more than likely you have a line in the code that is killing the server or just making it give up parsing the PHP.

This could be a particular extension that's being used by that page or it could be another killbot function that hobbles the server into just sitting there with its arms crossed.

Your error logs show that the last thing to happen before it shoves the save dialog in your face is a connect to the database. Follow the code back to that and make sure that's solid before moving onto the next possible troubleshooting breadcrumb that may or may not arise.

Since you can see the file with no problem on another set up, in this case easyPHP, the problem is very much on the XAMPP set up and a configuration that is being tripped up by the code.

Answer 4

I've encountered the exact same error. Make sure the mysql user privileges are set correctly.

Log in on the command line and confirm you are able to login, switch to the concerning database and view tables and records. Just login with command: 'mysql -u user -p' and fire off some queries.