How to troubleshoot a PHP script that causes a Segmenation Fault?
- by johnlai2004
I posted this on stackoverflow.com as well because I'm not sure if this is a programming problem or a server problem. I'm using ubuntu 9.10, apache2, mysql5 and php5.
I've noticed an unusual problem with some of my php programs. Sometimes when visiting a page like profile.edit.php, the browser throws a dialogue box asking to download profile.edit.php page. When I download it, there's nothing in the file. profile.edit.php is supposed to be a web form that edits user information.
I've noticed this on some of my other php pages as well. I look in my apache error logs, and I see a segmentation fault message:
[Mon Mar 08 15:40:10 2010] [notice] child pid 480 exit signal Segmentation fault (11)
And also, the issue may or may not appear depending on which server I deploy my application too.
Additonal Details
This doesn't happen all the time though. It only happens sometimes. For example, profile.edit.php will load properly. But as soon as I hit the save button (form action="profile.edit.php?save=true"), then the page asks me to download profile.edit.php. Could it be that sometimes my php scripts consume too much resources?
Sample code
Upon save action, my profile.edit.php includes a data_access_object.php file. I traced the code in data_access_object.php to this line here
if($params[$this->primaryKey])
{
$q = "UPDATE $this->tableName SET ".implode(', ', $fields)." WHERE ".$this->primaryKey." = ?$this->primaryKey";
$this->bind($this->primaryKey, $params[$this->primaryKey], $this->tblFields[$this->primaryKey]['mysqlitype']);
}
else
{
$q = "INSERT $this->tableName SET ".implode(', ', $fields);
}
// Code executes perfectly up to this point
// echo 'print this'; exit; // if i uncomment this line, profile.edit.php will actually show 'print this'. If I leave it commented, the browser will ask me to download profile.edit.php
if(!$this->execute($q)){ $this->errorSave = -3; return false;}
// When I jumped into the function execute(), every line executed as expected, right up to the return statement.
And if it helps, here's the function execute($sql) in data_access_object.php
function execute($sql)
{
// find all list types and explode them
// eg. turn ?listId into ?listId0,?listId1,?listId2
$arrListParam = array_bubble_up('arrayName', $this->arrBind);
foreach($arrListParam as $listName)
if($listName)
{
$explodeParam = array();
$arrList = $this->arrBind[$listName]['value'];
foreach($arrList as $key=>$val)
{
$newParamName = $listName.$key;
$this->bind($newParamName,$val,$this->arrBind[$listName]['type']);
$explodeParam[] = '?'.$newParamName;
}
$sql = str_replace("?$listName", implode(',',$explodeParam), $sql);
}
// replace all ?varName with ? for syntax compliance
$sqlParsed = preg_replace('/\?[\w\d_\.]+/', '?', $sql);
$this->stmt->prepare($sqlParsed);
// grab all the parameters from the sql to create bind conditions
preg_match_all('/\?[\w\d_\.]+/', $sql, $matches);
$matches = $matches[0];
// store bind conditions
$types = ''; $params = array();
foreach($matches as $paramName)
{
$types .= $this->arrBind[str_replace('?', '', $paramName)]['type'];
$params[] = $this->arrBind[str_replace('?', '', $paramName)]['value'];
}
$input = array('types'=>$types) + $params;
// bind it
if(!empty($types))
call_user_func_array(array($this->stmt, 'bind_param'), $input);
$stat = $this->stmt->execute();
if($GLOBALS['DEBUG_SQL'])
echo '<p style="font-weight:bold;">SQL error after execution:</p> ' . $this->stmt->error.'<p> </p>';
$this->arrBind = array();
return $stat;
}
