04.17.09
Posted in CakePHP, MySQL, PHP, Web Development at 3:15 pm by BrianS
As of cakePHP 1.2.1.8004 you can’t use CURRENT_TIMESTAMP as the default for a column. With MySQL when the default is set to CURRENT_TIMESTAMP the current date+time is inserted for a new row that doesn’t specifically define the value of the column.
From what I can tell, when CakePHP specifies the values for all columns when it creates a new record. A column with a defined default that is not specifically set by the user is manually set by CakePHP (rather than let MySQL handle defaults upon record insertion). But CakePHP doesn’t understand the CURRENT_TIMESTAMP keyword and so treats it as a string and wraps it in quotes. This breaks the resulting INSERT statement and you receive an error:
Incorrect datetime value: ‘CURRENT_TIMESTAMP’
Interestingly, columns that are named “created” and “modified” receive special handling by CakePHP. These columns are treated like auto-update columns by CakePHP and it sets them as expected. With the special handling of these columns in mind it is possible to get around the CURRENT_TIMESTAMP bug by following the recommended settings for created/modified columns, i.e. specifying the field as DATETIME with a default of NULL. CakePHP will automatically update the columns when inserting/updating records.
References:
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01.15.09
Posted in CakePHP, PHP, Web Development at 2:44 pm by BrianS
I’m still learning CakePHP. My most recent experimentation is with forms and URL redirecting. In the process I noticed that if the URL includes an ampersand, even in URL-encoded form, CakePHP will read in the URL incorrectly.
In my case, I was taking a form submission and redirecting it to a new page, appending the submitted data as URL parameters (e.g. of the form /controller/action/name:value). CakePHP handles ampersand in POST-submitted forms just fine, but during the redirect I noticed that the value of the parameter was cut off at the ampersand. For example, I’m creating a search form for a list of items (located at /items/index). When you submit the form with a value of “ball & chain” the controller sees it just fine. The form is submitted to the search action (/items/search) which takes the values, constructs a new URL, and redirects back to the item list (/items/index/Search.keywords:ball+%26+chain). However, the index action only sees “ball ” … the rest of the value is assumed to be additional key/value pairs in the querystring.
This problem seems like a pretty major issue to me. A bug report has already been filed, but I don’t believe it will be addressed anytime soon. And for good reason, the bug is actually in Apache’s mod_rewrite module rather than in CakePHP. When mod_rewrite processes a URL it unescapes any escaped characters (newer releases unescape to two levels). What this means for CakePHP is that any escaped characters in the URL become normal characters in the querystring (%26 becomes &).
The best overview of the problem has a good work-around, but it requires modification of the core CakePHP scripts. I’ll leave that to the experts. On our install I’ve found that a triple-escaped value will only be unescaped twice, resulting in the proper escaping after being parsed by mod_rewrite.
References
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11.21.08
Posted in MySQL, PHP, Web Development at 2:28 pm by BrianS
With a large set of test packets in need of transcription, little time to do so, and even less desire to spend the money on temporary workers, I needed to think of some other way to perform the task. Luckily I was able to come up with a method using a tool from Amazon that proved relatively easy to implement. Mechanical Turk .
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08.14.08
Posted in PHP, System Administration at 4:32 pm by BrianS
I needed to do a mass resampling of around 280,000 images. There are a number of ways to do this, but I settled on doing it via PHP because the images are stored on our web server, the total size of the images is large (~10GB), and I didn’t want to kill my machine trying to get it done.
PHP is ideal for a task such as this: parsing directories and subdirectories for images is easy; resampling using the built-in library (GD) is a breeze; specifying the destination as a subdirectory is simple. The one minus was processor usage. Performing image manipulation eats up the CPU in a big way.
Luckily linux systems have a built-in utility for addressing a situation like this: nice. nice will “run a program with modified scheduling priority.” I’m running the image manipulation script using the following command:
nice --adjustment=19 php script.php
If nothing else is going on the script will use whatever resources are available. When anything with a higher priority executes, that program will take precedence over the script with regard to system resources. The script should thus not affect the responsiveness of the web server. This is the reason I was searching for this kind of functionality.
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06.19.08
Posted in PHP, Web Development at 3:13 pm by BrianS
I was tasked with creating a demonstration of a dynamically generated graph for one of the grant proposals being worked on at present. This isn’t something we’ve really done before in PHP, but I had a feeling it would not be a unique requirement. A quick search revealed that a PEAR package exists for just this purpose: Image_Graph.
Installation was not too difficult, though I did have to ensure that a few dependencies were installed before PEAR would load the package. Documentation for the module is not that great, but there are a number of samples and a fairly active discussion forum.
I did not find the graphing object very intuitive. It seems to me that a lot of the properties and functions are abstracted from the objects they affect. I suspect this was a design decision to allow for greater flexibility, but it may also be due to an older coding style. The current branch appears to have been developed in earnest starting in 2005, and it’s been a few years since a new release. Even so, my initial exposure leads me to believe the package may be stable enough for even a production-level project so long as sufficient QA has been performed.
It took me only a couple of days to hack together the demonstration. Though the requirements of the script were few, I decided to push the limits of my object-oriented PHP and create the graphing component as a class. Overall it was a good first-try at producing something of this nature. You can find the demonstrator at http://flora.p2061.org/weather_data/.
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06.18.08
Posted in PHP, Web Development at 5:05 pm by BrianS
Piloting packets for this year are starting to come in and the data from these packets needs to be entered into the items utility. Because the questions in the packet have changed from previous years, and due to the rigid structure of the piloting data entry form and data tables, I decided to rewrite the data entry form. The new format allows more flexible on the front-end without requiring modification of the back-end. In addition I modified the way PHP interacts with the packet data from MySQL by utilizing a structured array to hold the data.
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05.21.08
Posted in PHP, System Administration at 3:25 pm by BrianS
I recently wanted to update our install of WordPress to the latest version. WordPress is a fairly easy install, and we could learn a thing or two about application set-up by examining their code. But I recently switched to using subversion to deploy and maintain our install. In just the little bit I’ve used subversion so far, I believe development and deployment of our internal applications would be simplified by employing it for all our projects. Here’s a quick outline of the process, with examples based on my WordPress deployment.
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05.14.08
Posted in MySQL, PHP, Web Development at 11:54 am by BrianS
While working on the Benchmarks search I wanted to try and provide a feature I find useful on Google and other search engines: word form expansion (lemmatisation). A little research showed to me that this would require more work than we really should be spending on search functionality. Especially considering that the built-in MySQL full text search capability is sufficient for our needs. So I decided to focus on a feature that would still provide value but require little time: word stem expansion.
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05.13.08
Posted in PHP, Web Development at 4:09 pm by BrianS
I made a few updates to the school reports at the request of the researchers.
- Added a save feature so that packet/item selections for a report can be retrieved at a later date.
- Added the ability to set thresholds that must be met before the script will include statistics in the report.
- Updated tables to reflect changes in displayed information and formatting.
In regards to the above changes, the save feature is of particular note for it inscrutibility. While the technique used to save/retrieve the report setting is adequate, the code to enable this functionality is not well-implemented. Unfortunately, time constraints required a fast, rather than best, implementation.
As modifications are requested this script is getting to be a little harder to work with. The code was created over the course of a week or two back in January. I was able to make quick work of it by using some concepts I initially worked out for summary table generation (and based on discussions with Brian W). While the data is stored in a psuedo object-oriented format, the script itself is fairly linear in design. If more modifications are requested the script may need some rewrites to enable a bit more flexibility.
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03.18.08
Posted in PHP, Web Development at 2:22 pm by BrianS
The number produced by summary table 8 in the items utility were not quite correct. The researchers noted that the means by which calculation of answer selection was performed was not quite as they wanted it.
Luckily table 8 uses a new summary table generation technique I borrowed from the school reports. The data, display, and summarization code is segregated to a certain degree (though not as much as would be preferred). This allows me to update one aspect of the script without having to monkey around too much with other aspects.
The data is currently stored in a data array that is organized to allow for relatively easy access. The summary information is currently compiled inline in the code. While this isn’t ideal, the method used (summary arrays) should allow for better segregation in the future. The calculation of concern is stored in its own function, answer_selected(). That function includes some basic versioning capability and so I was able to add a new version of the calculation that matches the researchers expectation without changing anything else in the code.
I think a modification of this technique would work well for all tables in the utility and should not require significant investment in development time. As additional tables need work I may investigate adding them as components of the new summary table script (summary_table.php).
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