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Database I-O
Accessing a database isn't just for storing numbers and compiling statistics (although it is certainly useful doing that). A database can also be used to store user information (such as logins and passwords), posts in the case of a forum, or articles in the case of a blog. You could even go really crazy and store your entire site as a database, simply using PHP to extract the necessary information. Of course, before you get any of this information you will need to connect to the database.$connection=mysql_connect(servername, username, password);
mysql_select_db(database_name,$connection);
servername is the location of the database - usually "localhost" will be it.
username and password are exactly what you think they'd be - the username and password to access the database. If there is a failure in connecting to the database for some reason (such as incorrect login credentials), mysql_connect will return false. After we are connected, we run mysql_select_db to select the actual database (as there can be many different databases on a server). We pass in the name of the database (database_name) and $connection, and we are ready to run queries:
$query="<MySQL query>"
$result=mysql_query($query);
Finally, we will want to access each row of our results - which we do using the following bit of code:
while ($row=mysql_fetch_array($result))
{
<Code for this specific row>
}
row will be an associative array, with keys being the names of each of the result columns - so if you have a database table named "PEOPLE" which looks like this:
| FName | LName | Age |
|---|---|---|
| Alex | Smith | 29 |
| Bonnie | Johnson | 35 |
| Carlos | Williams | 18 |
| Danielle | Jones | 13 |
| Erica | Brown | 49 |
| Fred | Davis | 62 |
And your MySQL query was "SELECT * FROM PEOPLE", one iteration of mysql_fetch_array() might look something like:
- $result['FName']='Alex';
- $result['LName']='Smith';
- $result['Age']=29;
For the complete set of MySQL-related functions, see the PHP manuaul at www.php.net.
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