Question

Let me start by explaining.
I have a few global database connections and have a few simple functions that use each one and perform queries and such.

Because i want to use the connections more then once, and to save me defining them each time in each function i have created them as globals at the top of the document.
However i am just wondering that instead of having to write

global $mysql_db1, $mysql_db2, $mysql_db3, $mysql_db4, $mysql_db5;

Is there anyway to make this happen without me having to copy and paste it each time?

I know its trivial but i just wanted to speed up my own development,

Answer 1

Globals are usually regarded as bad practice. I won’t pontificate at you about it, but check out this article: http://blog.case.edu/gps10/2006/07/22/why_global_variables_in_php_is_bad_programming_practice

You can use the $GLOBALS superglobal to access any variable that has been defined in the global scope (docs). Thus, in your example code, simply using $GLOBALS['mysql_db1'] would be the equivalent of having the line global $mysql_db1; and then using $mysql_db1.

I cannot stress enough (without pontificating) how bad of a plan this is. YOU might be all right with it the entire time you’re developing, but poor poor Johnny Nextguy, and may the Gods of Code save you if you include a third-party script that also uses globals… and there’s a conflict of variable names. Now you’re in for it!

As has been suggested, you are better off encapsulating your database functionality in a class. If you use a static class, you still have all the benefits of a global variable without a polluted scope or danger of overwriting.

Here is a sample database class, along with usage:

// put this in a library file or some place that all scripts include
require_once('database_class.php');
$db = new db(array(
 'host'=>'localhost'
 'user'=>'db_user_name'
 'password'=>'db_password',
 'database_name'=>'my_database'
));


// now anywhere in code you want to use it
$array = db::getRows('SELECT id, name FROM users');
$field = db::getField('SELECT name FROM users WHERE id=10');


<?php
// database_class.php
class db {
    static protected $resource_link = null;

    function __construct($args=false) {
        if ($args===false || !is_array($args))
            return false;
        if (
            !isset($args['host']) ||
            !isset($args['user']) ||
            !isset($args['password']) || 
            !isset($args['database_name'])
        )
            return critical_error('Missing database configuration data.');


        self::$resource_link = @mysql_connect($args['host'],$args['user'],$args['password']);
        if (!self::$resource_link)
             return critical_error('Error connecting to database 2001.  MySQL said:<br>'.mysql_error());
        @mysql_select_db($args['database_name'],  self::$resource_link);
        return;
    }


    // return a single-dimmension array of fields as string
    static public function getFields ($sql=false, $field=false) {
        $res = null;
        if ($sql!==false) {
            $query_obj = mysql_query($sql, self::$resource_link);
            if ($query_obj) {
                $res = array();
                 while ($this_row = mysql_fetch_array($query_obj)) {
                    if ($field !== false && isset($this_row[$field]))
                        $res[] = $this_row[$field];
                    else
                        $res[] = $this_row[0];
                }
            } // end :: if query object is not null
        } // end :: if $sql is not false
        return $res;
    }

    // return a single-dimmension array of fields as string with keyfield as key
    static public function getKeyFields ($sql=false, $key_field='id', $list_field='id') {
        $res = null;
        if ($sql!==false) {
            $query_obj = mysql_query($sql, self::$resource_link);
            if ($query_obj) {
                 while ($this_row = mysql_fetch_array($query_obj)) {
                    if (isset($this_row[$key_field]))
                        $res[$this_row[$key_field]] = $this_row[$list_field];
                }
            } // end :: if query object is not null
        } // end :: if $sql is not false
        return $res;
    }

    // return a single field as string from the first row of results
    static public function getField ($sql=false) {
        $res = null;
        if ($sql!==false) {
            $query_obj = mysql_query($sql, self::$resource_link);
            if ($query_obj) {
                $this_array = mysql_fetch_array($query_obj);
                if (is_array($this_array))
                    return $this_array[0];
            } // end :: if query object is not null
        } // end :: if $sql is not false
        return $res;
    }

    // return a single row as an array
    static public function getRow ($sql=false) {  
        $res = null;
        if ($sql!==false) {
            $query_obj = mysql_query($sql, self::$resource_link);
            if ($query_obj)
                $res = mysql_fetch_assoc($query_obj);
        } // end :: if $sql is not false
        return $res;
    }

    // return an array of rows as arrays of strings
    static public function getRows ($sql=false) {
        $res = null;
        if ($sql!==false) {
            $query_obj = mysql_query($sql, self::$resource_link);
            $res = array();
            if ($query_obj) {
                 while ($this_row = mysql_fetch_assoc($query_obj)) {
                    $res[] = $this_row;
                }
            } // end :: if query object is not null
        } // end :: if $sql is not false
        return $res;
    }

    // return an array of rows as arrays of strings, using specified field as main array keys
    static public function getKeyRows ($sql=false, $key_field='id', $include_key_in_results=true) {
        $res = null;
        if ($sql!==false) {
            $query_obj = mysql_query($sql, self::$resource_link);
            if ($query_obj) {
                $res = array();
                 while ($this_row = mysql_fetch_assoc($query_obj)) {
                    if (isset($this_row[$key_field])) {
                        $res[$this_row[$key_field]] = $this_row;
                        if ($include_key_in_results == false)
                            unset($res[$this_row[$key_field]][$key_field]);
                    } // end :: if checking for key field in result array
                } // end :: while looping query obj
            } // end :: if query object is not null
        } // end :: if $sql is not false
        return $res;
    }


    // do an update query, return true if no error occurs
    static public function update ($sql=false) {
        $res = false;
        if ($sql!==false) {
            $query_obj = mysql_query($sql, self::$resource_link);
            if ($query_obj && strlen(mysql_error()) < 1)
                $res = true;
        }
        return $res;
    }

    // do an insert query, return the auto increment ID (if there is one)
    static public function insert ($sql=false) {
        $res = null;
        if ($sql !== false) {
            $query_obj = mysql_query($sql, self::$resource_link);
            if ($query_obj)
                $res = mysql_insert_id(self::$resource_link);
        }
        return $res;
    }    
}
?>