PHPLib and Multiple Databases Page 3

Expanding PHPLIB

PHPLIB accesses databases through an object created from class DB_Sql.
Db_mysql.inc includes the DB_Sql class as modified for MySQL. We will
extend DB_Sql by adding code to common.php3, after the line that includes
db_mysql.inc.

DB_Sql contains many functions to perform queries. The one we want to
change is:

<?php
 /* public: connection management */
function connect($Database = "", $Host = "", $User = "", $Password = "") {
    /* Handle defaults */
    if ("" == $Database)
        $Database = $this->Database;
    if ("" == $Host)
        $Host     = $this->Host;
    if ("" == $User)
        $User     = $this->User;
    if ("" == $Password)
        $Password = $this->Password;
    /* establish connection, select database */
    if ( 0 == $this->Link_ID ) {
         $this->Link_ID=mysql_pconnect($Host, $User, $Password);
        if (!$this->Link_ID) {
            $this->halt("pconnect($Host, $User, $Password) failed.");
            return 0;
        }
        if (!@mysql_select_db($Database,$this->Link_ID)) {
            $this->halt("cannot use database ".$this->Database);
            return 0;
        }
    }
    return $this->Link_ID;
}
?>

Find the connect() function in your db_mysql.inc (or the .inc for your
database), then copy it in to common.php3 somewhere after the include of
db_mysql.inc. You will have to wrap it in a class definition as described
at the end of this article.

I find the code hard to read. Therefore, the first thing to do is make the copied code
readable:

<?php
/* public: connection management */
function connect($Database = "", $Host = "", $User = "", $Password = "") {
    /* Handle defaults */
    if ("" == $Database) {
        $Database = $this->Database;
    }
    if ("" == $Host) {
        $Host     = $this->Host;
    }
    if ("" == $User) {
        $User     = $this->User;
    }
    if ("" == $Password) {
        $Password = $this->Password;
    }
    /* establish connection, select database */
    if ( 0 == $this->Link_ID ) {
        $this->Link_ID=mysql_pconnect($Host, $User, $Password);
        if (!$this->Link_ID) {
            $this->halt("pconnect($Host, $User, $Password) failed.");
            return 0;
        }
        if (!@mysql_select_db($Database,$this->Link_ID)) {
            $this->halt("cannot use database ".$this->Database);
            return 0;
        }
    }
    return $this->Link_ID;
}
?>

I indented the code so the levels let me match the brackets, with the
enclosed code. This avoids errors caused by missing brackets. I added
brackets to single lines. PHP lets you get away without brackets around
single lines of code after if statements. As soon as you add extra code,
the shortcut fails. I suggest always use the brackets to avoid errors when
you add code later.