WordPress development tutorials

To get the column names for a MySQL database table in WordPress, use the following:

global $wpdb;

$table_name = $wpdb->prefix . 'posts';

foreach ( $wpdb->get_col( "DESC " . $table_name, 0 ) as $column_name ) {
  error_log( $column_name );
}

Which will result in something like the following being printed to your debug.log:

ID

post_author

post_date

post_date_gmt

post_content

...

You get the idea 🙂

Tutorials WordPress Development January 14, 2013

Published by Justin Stern

Justin is one of our co-founders, and is our resident overengineer. He likes to write developer tutorials and make black magic happen in our plugins. He thinks that writing code is a lot easier than writing words.

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3 Comments

  1. moslem

    This is a trick that shows you so clever to extract column name with all weakness of wordpress;
    I think this is only way.
    thanks.

  2. simba

    I assume this method works correctly and has been tested, but somehow for me it doesn’t return the names of each column.
    Does this perhaps have anything to do with wordpress not being abled to handle customly created tables?
    It returns NULL for each column name, however it does return the exact amount of columns I have stored in my custom table in the database.

    I altered wp-db.php to debug the prepare function to see if anything went wrong with my query.

    This is the code I’ve setup:

    function prepare( $query, $args = null ) {
    if ( is_null( $query ) )
    return;

    if ( func_num_args() < 2 )
    _doing_it_wrong( 'wpdb::prepare', 'wpdb::prepare() requires at least two arguments.', '3.5' );

    $args = func_get_args();
    array_shift( $args );
    // If args were passed as an array (as in vsprintf), move them up
    if ( isset( $args[0] ) && is_array($args[0]) )
    $args = $args[0];
    $query = str_replace( "'%s'", '%s', $query ); // in case someone mistakenly already singlequoted it
    $query = str_replace( '"%s"', '%s', $query ); // doublequote unquoting
    $query = preg_replace( '|(?<!%)%f|' , '%F', $query ); // Force floats to be locale unaware
    $query = preg_replace( '|(?<!%)%s|', "'%s'", $query ); // quote the strings, avoiding escaped strings like %%s
    array_walk( $args, array( $this, 'escape_by_ref' ) );
    echo "”;
    $test = vsprintf($query, $args);
    var_dump($test);
    echo “describe returns the following column names in table: ” . $this->form . “\n\r”;
    foreach ($this->get_col(“DESCRIBE ” . $this->form . “;”, 0) as $colum)
    {
    var_dump($column);
    }
    echo “”;
    return @vsprintf( $query, $args );
    }

    The query I’m currently having trouble with is:
    string(236) “INSERT INTO `wp_form` (`personeelsnummer`, `bsn_nummer`, `voornaam`, `voorletters`, `achternaam`, `geslacht`, `geboortedatum`) VALUES (‘123432414′,’weqr21341423′,’21341234′,’23423142′,’2134231432′,’Man’,’03/10/2013′)”

    The result from the function above is:
    describe returns the following column names in table: wp_form

    NULL
    NULL
    NULL
    NULL
    NULL
    NULL
    NULL
    NULL
    NULL
    NULL
    NULL
    NULL
    NULL
    NULL
    NULL
    NULL
    NULL
    NULL
    NULL
    NULL
    NULL
    NULL
    NULL
    NULL
    NULL
    NULL
    NULL
    NULL
    NULL
    NULL
    NULL
    NULL
    NULL
    NULL

    my database returns:
    Unknown column ‘personeelsnummer’ in ‘field list’

    When I execute describe in phpmyadmin on my table it shows:
    Showing rows 0 – 29 ( 34 total, Query took 0.0015 sec)
    Including the correct field names.
    I’ve been having trouble with this for days now, could you perhaps by sheer chance have a slight idea why that could be?

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