Category Archives: Web Development

PHP/Apache running on Linux won’t connect to a PostgreSQL server

SELinux will block PHP/Apache from connecting to PostgreSQL (and probably any other DB) by default on some Linux distributions. If you are trying to get PHP to connect to a PostreSQL DB on a linux box for the first time and you are sure your pg_hba.conf on the target box is setup correctly then try this:

setsebool -P httpd_can_network_connect 1

This should configure SELinux to allow Apache/PHP to connect to other hosts.

National Broadband Map Review

The National Telecommunications and Information Administration (NTIA) in collaboration with the FCC has published a series of broadband maps on a new site called National Broadband Map (NBM). These maps show what broadband services are available throughout the United States as well as other interesting broadband data.

national broadband map screenshot

Hit this link and click the “Explorer the Map” option on their main page to see a map of the US with shaded areas where selected broadband services are available. You can click different selections above the map to toggle the various broadband technologies. To see other maps such as advertised versus actual broadband speeds click on the “Show Gallery” option in the lower right hand corner.

Rochester, NY does pretty well on advertised versus actual although there a few slower than advertised points here and there. Upload performance data is also available. Usually the cable and DSL providers don’t brag much about upload performance likely because in most cases it is lousy compared to download performance. I think upload performance will become more important to the typical internet user than it as in the past now that people are sharing their pictures and video online.

The NBM site use a variety of open source technologies including:

  • JQuery – My favorite JavaScript library.
  • Modernizr – A JavaScript library to detect browser capabilities.
  • OpenLayers – Provides a JavaScript API to display WFS and WMS GIS layers.
  • GeoServer – A Java based server software that provides WFS and WMS services.

What is particularly interesting about the site is the developer resources. They provide a series of API’s you can call from your own web applications to use their data. Output formats include XML, JSON, and JSONP implementations. If you want to use the data locally without the APIs you can download it.

I do have a couple criticisms regarding the maps and ironically, they are bandwidth related. The first is that there are too many tiles returned when viewing the default map of the US. I noticed the map was a little slow to fill in. When I enabled Firebug and clicked on the “Explore the Map” option off the main page, over 500 tiles were pulled down. In fact, Firefox/Firebug became unresponsive. I would expect less than 30 256×256 tiles need to be pulled down for a reasonably sized browser window. I wager there is something goofy going on like a bounding box not set for the area displayed.

My second criticism is that the site is not using gzip to compress JavaScript files. Modern web applications tend to lay on the JavaScript pretty heavy and this one is no exception. OpenLayers.js is nearly 1MB all by itself. By enabling gzip on sites with large JavaScript files you can significantly improve site performance. This is a good topic for a future post.

Overall I think the National Broadband Map Site is an excellent resource. It provides very useful data on broadband technologies/speeds, makes this data available via APIs or download, and also demonstrates a variety of open source web application technologies.

Is it worth the $20 million that contractors were paid to build the map? I would say certainly not at first glance but I would want to hear the whole story before I jump to conclusions. I.e. how much of that $20 million was spent on actual development? I am much more skeptical of the alleged $293 million required to collect the data.

Titanium Appcelerator Quirks (Updated)

I recently started tinkering with the Appcelerator Titanium Development Platform and have run into a couple quirks.

Web Inspector will not Launch

If you create a Titanium project on any drive other than C:\ on a Windows system, you will not be able to launch the Web Inspector. This is a apparently a known bug in Titanium Developer.

Conflicting PHP Installations

If you attempt to launch a Titanium Appcelerator PHP app in Titanium Developer on a Windows system that already has a local PHP installation, you may see the following error:

Kroll Event Window Instance: YourApp.exe – System Error

The program can’t start because php_mbstring.dll is missing from your computer. Try reinstalling the program to fix this problem.

Titanium Appcelerator php_mbstring.dll error

Don’t bother re-installing anything. What is likely happening is that your pre-existing PHP installation added a “PHPRC” environment variable that points to your existing PHP install folder. I think Titanium’s command line PHP instance sees this variable and then attempts to use the php.ini file in that path. Your existing PHP installation folder does not likely have the PHP settings and/or module paths that Titanium needs so it breaks.

To fix this without renaming your current PHP installation folder you can delete the “PHPRC” environment variable. Your existing PHP installation should work fine without it because PHP will look for the php.ini file in the same folder it is running from. To delete the “PHPRC” environment variable on Windows 7, click Windows Start, right click “Computer”, left click “Properties” -> “Advanced system settings” -> “Environment Variables…” -> select “PHPRC” under “System variables”, and then click “Delete”.

how to delete the phprc environment variable

Hopefully you can now launch your Titanium application without an error and your existing PHP installation will continue to work normally.

Php-cgi.exe application error on IIS with FastCGI

I recently installed PHP 5.2.14 on a Windows 2003 machine running IIS 6 with FastCGI to do some PHP testing at home. I chose the fast CGI install and added several extensions during the install including Curl and Oracle. When I attempted pull a test page after the install completed, I saw the following php-cgi.exe application error on the Windows server’s desktop:

The instruction at “0x100f36ec” referenced memory at “0x000c0194″. The memory could not be “read”.

IIS sent the following error message back to the requesting browser after a couple minutes:

FastCGI Error
The FastCGI Handler was unable to process the request.

Error Details:

* The FastCGI process exited unexpectedly
* Error Number: -1073741819 (0xc0000005).
* Error Description: Unknown Error

HTTP Error 500 – Server Error.
Internet Information Services (IIS)

After some trial and error I was able to get my test page to display if I commented the “extension=php_curl.dll” and “extension=php_oci8.dll” lines in my php.ini file:

; Local Variables:
; tab-width: 4
; End:
[PHP_CURL]
;extension=php_curl.dll
[PHP_GD2]
extension=php_gd2.dll
[PHP_MSQL]
extension=php_msql.dll
[PHP_MSSQL]
extension=php_mssql.dll
[PHP_MYSQL]
extension=php_mysql.dll
[PHP_MYSQLI]
extension=php_mysqli.dll
[PHP_OCI8]
;extension=php_oci8.dll
[PHP_PDO]
extension=php_pdo.dll
[PHP_PGSQL]
extension=php_pgsql.dll
[PHP_SHMOP]
extension=php_shmop.dll
[PHP_SOAP]
extension=php_soap.dll
[PHP_SQLITE]
extension=php_sqlite.dll
[PHP_XMLRPC]
extension=php_xmlrpc.dll

After some more trial error I was unable to get PHP to work without leaving the two lines commented. I tried both the VC6 thread and VC6 non thread safe versions and both exhibited the same behavior. On the PHP download page there is a “Which version do I choose?” section that basically explains that I should be using the VC9 version for IIS. Unfortunately I only saw the PHP 5.3.3 VC9 download and I wanted to test with PHP 5.2.14.

I downloaded PHP 5.3.3 anyway and it worked. I guess I will be testing with PHP 5.3.3.

On a somewhat related note, if you are using FastCGI with IIS, you will probably want the VC9 PHP 3.3.3 non thread safe version. This article explains why.

How to get the contents of an Oracle CLOB data field in PHP

The Oracle “CLOB” (Character Large Object) is a data type used to store up to 4 Gigabytes of text. Retrieving the contents of a CLOB is not as intuitive as you might think.

Let’s say you have a CLOB field/column named “mychars” in an Oracle DB table named “mytable” along with some other fields. You want to simply echo out the text in the “mychars” field:

<?php
    $id = '3';
    $conn = oci_connect('myusr', 'mypass', 'mydb');
    if (!$conn){
        echo 'Connection error.';
    }
    $sql = 'SELECT * FROM mytable WHERE myid=:id';
    $stid = oci_parse($conn, $sql);
    oci_bind_by_name($stid, ":id", $id);
    $result = oci_execute($stid);
    if($result !== false){
        while($row = oci_fetch_assoc($stid)){
            echo $row['mychars'];
        }
    }
?>

The above code will give you an error that looks like the following:

Catchable fatal error: Object of class OCI-Lob could not be converted to string in somefile.php on line 14

If you try to do a print_r() on the CLOB in an attempt to figure out what you are dealing with you will get something that looks like:

OCI-Lob Object ( [descriptor] => Resource id #3 )

This is because a Lob object is returned instead of the contents of the CLOB.

To get the CLOB contents you will need to call the load() or read() methods on the returned object. The latter will require the length of data to read in bytes but has the advantage of not being limited by the script memory limit:

<?php
    $id = '24382';
    $conn = oci_connect('myusr', 'mypass', 'mydb');
    if (!$conn){
        echo 'Connection error.';
    }
    $sql = 'SELECT * FROM mytable WHERE myid=:id';
    $stid = oci_parse($conn, $sql);
    oci_bind_by_name($stid, ":id", $id);
    $result = oci_execute($stid);
    if($result !== false){
        while($row = oci_fetch_assoc($stid)){
            echo $row['mychars']->load();
            //or
            echo $row['mychars']->read(2000);
        }
    }
?>