Archive for the ‘PHP/mySQL’ Category

SOLVED: WordPress pages 404 Error on new server

November 27th, 2012

I ran into this problem recently when moving a client’s WordPress site to a new server. On the old server, all of the pages had permalinks set up and they worked great. After moving the site, none of the pages were working, except the home page. All of the other pages gave me a 404 error. The admin pages worked fine.

When diagnosing this issue, you need to check a few things. First, check that your admin panel is still working when you log in. If not, you may have a problem with your base urls in the database. To check this, log into your phpmyadmin panel and check the wp_options table in the database. There are 2 entries that contain the site url. Make sure that they are correct.

Assuming that your admin panel is working, the issue is probably a server setting causing a problem with the Permalinks. To check this, go to the Settings>Permalinks page and change the setting to Default. Now, go back to your homepage and see if your pages are working. The permalinks will NOT work, but you should be able to click around using the navigation.

If your pages now work, then the problem is that mod_rewrite is not enabled correctly on the new server. If you want to check this, simply create a new htaccess file with the following code:

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /wp/
RewriteRule ^test\.html [QSA,L]

*note that your RewriteBase will be different than mine.

Now, go to your WordPress site and try to navigate to test.html. It should redirect you to the Google. If not, then mod_rewrite is definitely not working and you need to have your server admin or hosting company fix it.

I found a lot of people with the same issue when I was trying to fix this, but no one seemed to have a solution. Hopefully, this will help.

Querying the wordpress database with $wpdb from PHP

September 19th, 2012

I have been working with WordPress a lot lately and I really like it. I want to have 10,000 of it’s babies. I recently needed to access the database using the $wpdb class that is built in to wordpress, but my PHP file was not part of the wordpress core, so $wpdb wasn’t automatically available. It’s really useful for accessing info like the root URL of your site (stored in the wp_options table). If you are creating a plugin or custom feature and need access to the database, it can be hard to figure how to enable the $wpdb class in your PHP files. Luckily, the code is actually not that complicated. The first thing you have to do is include the necessary files at the top of your custom php file:

include_once '/wp-load.php';
//$wpdb is now accessible!

If you uncomment the var_dump line in the code above and run this php file, it should spit out a lot of information. If it doesn’t, then you aren’t including the wp-load.php file correctly. You must have WordPress 3.0 or higher installed and your PHP file must be installed somewhere in the same directory as WordPress. You can also use a relative path if you need to:

include_once '../../../wp-load.php';
//$wpdb is now accessible!

Just make sure you have your relative path correct. It may be different, depending on where your PHP file is located in your wordpress installation.

Now that you have the $wpdb class enabled, you can query the database. Going back to my example above, if you need to retrieve your site URL, you could add the following lines to the PHP file we just created:

$table_name = $wpdb->prefix . "options";
$sql = "SELECT option_value FROM ".$table_name." WHERE option_name = 'siteurl';";
$root_url = $wpdb->get_var($sql);

This uses the get_var() function of $wpdb to return a single item (your site url) from the wp_options table. Notice that on the first line, I also used the $wpdb->prefix property, which in almost all cases, will be “wp_”.

What if you wanted to run a mySQL query on a table? That’s simple too! just use the query() method of $wpdb. For example, we can insert values into a custom table that we created for a plugin:

$table_name = $wpdb->prefix . "my_custom_table";

$sql = "INSERT INTO ".$table_name." (
              ) VALUES (
                'some value',
                'some other value'
$result = $wpdb->query($sql) or die(mysql_error());
//do something with the result here

You can even do more complex things, like create the tables you need for a plugin. The following function runs a mySQL query to create a table for a plugin:

function create_my_custom_table() {
    global $wpdb;
    $table_name = $wpdb->prefix . "my_custom_table";
    global $my_custom_db_table_version;
    $installed_ver = get_option( "my_custom_db_table_version" );
    //Check if the table already exists and if the table is up to date, if not create it
    if($wpdb->get_var("SHOW TABLES LIKE '$table_name'") != $table_name || $installed_ver != $my_custom_db_table_version ) {
        $sql = "CREATE TABLE " . $table_name . " (
              id mediumint(9) NOT NULL AUTO_INCREMENT,
              field_1 varchar(100),
              field_2 varchar(100),
              UNIQUE KEY id (id)

        require_once(ABSPATH . 'wp-admin/includes/upgrade.php');
        update_option( "my_custom_db_table_version", $my_custom_db_table_version );
    //Add database table versions to options
    add_option("my_custom_db_table_version", $my_custom_db_table_version);

The code above is actually a function that will check the wp_options table for a field called “my_custom_db_table_version.” If it exists, it compares the value to a global variable $my_custom_db_table_version. If there is a newer version of the table or if the version can’t be found in the database, it creates/updates the custom table.

As with most things, wordpress makes it easier once you know the basic code. Good Luck!

HTML Multi checkbox set – the correct way to group checkboxes

February 15th, 2012

I was setting up an HTML form today and I wanted to group some options together in a multi checkbox set, allowing a user to select multiple options in a category. I usually just give each checkbox a unique name and parse all of the individual values in PHP, but this has always struck me as an ugly way to handle this use case.

As I was looking up the syntax for an HTML checkbox, I found a lot of info that said I could simply name all of the checkboxes the same and it would group all of the values together like this:

<input type="checkbox" name="chk_group" value="value1" />Value 1<br />
<input type="checkbox" name="chk_group" value="value2" />Value 2<br />
<input type="checkbox" name="chk_group" value="value3" />Value 3<br />

But this doesn’t work. When you POST the values to PHP, you only receive the last item selected in the group. The annoying thing is that a lot of the examples online show this same syntax even though it’s clearly wrong. After digging a little deeper, I found this forum post with the correct syntax. Adding square braces to the checkbox name creates an array of the selected values in the group:

<input type="checkbox" name="chk_group[]" value="value1" />Value 1<br />
<input type="checkbox" name="chk_group[]" value="value2" />Value 2<br />
<input type="checkbox" name="chk_group[]" value="value3" />Value 3<br />

This can be retrieved in PHP with a simple loop:

if (isset($_POST['chk_group'])) {
    $optionArray = $_POST['chk_group'];
    for ($i=0; $i<count($optionArray); $i++) {
        echo $optionArray[$i]."<br />";

Simple! I thought I should post this correct solution in the hopes that it might help someone else wade through all of the wrong information out there.

Prevent FCKEditor from converting image tags to input tags

December 2nd, 2011

FCK Editor is a free, open-source HTML editor that is commonly used in a variety of CMS (content management systems). It is often installed as a Drupal plugin and we use it in our own CMS at work. Unfortunately, it has a pesky default that converts image tags to input tags. If you add a linked image like this:

<a href=”…”><img src=”…” /></a>

it saves it as a linked input like this:

<a href=”…”><input type=”image” src=”…” /></a>

This can create CSS issues in some browsers because image inputs are displayed with a blue border. To prevent your image tags from being converted to input tags, you have to dig into the FCKEditor code and tweak it slightly. Every time I have to do this, it takes me an hour to find the code that needs to be changed. Hopefully, this will save someone else a lot of time and hassle…

1) Open this file:


2) Scroll down to about line 223. You will see this code:

if ( bImageButton )
	oImage = FCK.EditorDocument.createElement( 'INPUT' ) ;
	oImage.type = 'image' ;
	oImage = FCK.InsertElementAndGetIt( oImage ) ;
	oImage = FCK.CreateElement( 'IMG' ) ;

3) Change it to this:

if ( bImageButton )
	//oImage = FCK.EditorDocument.createElement( 'INPUT' ) ;
	//oImage.type = 'image' ;
	//oImage = FCK.InsertElementAndGetIt( oImage ) ;
	oImage = FCK.CreateElement( 'IMG' ) ;
	oImage = FCK.CreateElement( 'IMG' ) ;

problem solved! woo hoo!