How does this PHP know which array key/values to use? - php

Question

Below is part of a PHP database class someone else wrote, I have removed about 80% of it's code, all the un-related code to my question has been removed and just the amount remains that allows me to test this class without actually hitting a real database.
This class has a couple methods that let you set a key and value it then turns it into a mysql UPDATE and INSERT sql query using an array. I am trying to figure out how to use this code 100% so I can use this feature of it for UPDATE and INSERTS in my own application.
Basicly from what I gather you do something like this...
// assign some key/values to insert into DB
$db->assign('name', 'dfgd');
$db->assign('age', 87);
$db->assign('sex', 'female');
$db->assign('user_id', 4556);
// Do the insert
$db->insert('testing2');
Now where I am confused is I can keep on running code like this over and over on the page and it always will use the correct set of key/value array sets. Above you can see I used the assign() method 4 times and then call the insert() method which creates this
INSERT INTO test (name, age, sex, user_id) VALUES (jason davis, 26, male, 5345)
Now if I run another set like this on the same page...
// assign some key/values to insert into DB
$db->assign('name', 'dfgd');
$db->assign('age', 87);
$db->assign('sex', 'female');
$db->assign('user_id', 4556);
// Do the insert
$db->insert('testing2');
It then creates this...
INSERT INTO testing2 (name, age, sex, user_id) VALUES (dfgd, 87, female, 4556)
So how does it not combine the 2 sets of 4, so instead of inserting 8 record on the second insert, it completey replaces the first set of 4 values with the new set. This is great and what I want but I do not understand how it is happening? Also can this be improved anyway?
Below is a full class and my demo code, it can be ran without needing to connect to mysql for this demo, it will print to screen the SQL that it builds.
Also where would the public function reset() in the code below need to be used at, or would it not be needed?
<?php
class DB{
public $fields;
public function assign($field, $value){
$this->fields[$field] = ($value)==""?("'".$value."'"):$value;
}
public function assign_str($field, $value){
$this->fields[$field] = "'".addslashes($value)."'";
}
public function reset(){
$this->fields = array();
}
public function insert($table){
$f = "";
$v = "";
reset($this->fields);
foreach($this->fields as $field=>$value){
$f.= ($f!=""?", ":"").$field;
$v.= ($v!=""?", ":"").$value;
}
$sql = "INSERT INTO ".$table." (".$f.") VALUES (".$v.")";
//print SQL to screen for testing
echo $sql;
//$this->query($sql);
return $this->insert_id();
}
public function update($table, $where){
$f = "";
reset($this->fields);
foreach($this->fields as $field=>$value){
$f.= ($f!=""?", ":"").$field." = ".$value;
}
$sql = "UPDATE ".$table." SET ".$f." ".$where;
echo $sql;
//$this->query($sql);
}
public function query($_query){
$this->query = $_query;
$this->result = #mysql_query($_query, $this->link_id) or die( $_query."<p>".mysql_error($this->link_id) );
return $this->result;
}
public function insert_id(){
return #mysql_insert_id($this->link_id);
}
}
// start new DB object
$db = new DB;
// assign some key/values to insert into DB
$db->assign('name', 'jason davis');
$db->assign('age', 26);
$db->assign('sex', 'male');
$db->assign('user_id', 5345);
// Do the insert
$db->insert('test');
echo '<hr />';
// assign some key/values to insert into DB
$db->assign('name', 'dfgd');
$db->assign('age', 87);
$db->assign('sex', 'female');
$db->assign('user_id', 4556);
// Do the insert
$db->insert('testing2');
echo '<hr />';
// assign some key/values to UPDATE the DB
$db->assign('name', 'jason davis');
$db->assign('age', 26);
$db->assign('sex', 'male');
$db->assign('user_id', 5345);
// DO the DB UPDATE
$db->update('blogs', 'WHERE user_id = 23');
?>

Answer 1

Key in associative arrays are unique; assigning a new value erases the old.

Answer 2

If you still open for another database abstaction library, I want to suggest you to use AdoDB. It's can connect to multiple database, so you code will stay the same if you decide to switch database later. It have build in feature to sanitize data before insert/update.
For your code above, when you use AdoDB, you will write it like this:
$adodb =& ADONewConnection($dsn);
$data['name'] = 'dfgd';
$data['age'] = 87;
$data['sex'] = 'female';
$data['user_id'] = 4556;
// Do the insert
$result = $adodb->AutoExecute($table_name, $data, 'INSERT');
//If update, must have one of the key, such as id column
$result = $adodb->AutoExecute($table_name, $data, 'UPDATE', "id=$id");
You can read the documentation from the site, or inside zip file that you can download. I always use this library in all my project, even I prefer it more that build in CodeIgniter database library.

Answer 3

insert() and update() should (originally) set the $this->fields property back to an empty array upon execution, but you somehow (wrongly) deleted that code?
Update your code to this:
public function insert($table){
$f = "";
$v = "";
foreach($this->fields as $field=>$value){
$f.= ($f!=""?", ":"").$field;
$v.= ($v!=""?", ":"").$value;
}
$sql = "INSERT INTO ".$table." (".$f.") VALUES (".$v.")";
$this->reset();
//print SQL to screen for testing
echo $sql;
//$this->query($sql);
return $this->insert_id();
}
public function update($table, $where){
$f = "";
foreach($this->fields as $field=>$value){
$f.= ($f!=""?", ":"").$field." = ".$value;
}
$sql = "UPDATE ".$table." SET ".$f." ".$where;
$this->reset();
echo $sql;
//$this->query($sql);
}

Answer 4

Ok, we have come to the conclusion that my previous answer was right:
Because you use the name keys, it replaces the old keys with the new keys.
$db->assign('user_id', "1");
basically does this:
$this->fields['user_id] = (1)==""?("'1'"):1;
And when you got to do it again, it replaces it
$this->fields['user_id'] = (2)==""?("'2'"):2;
Try doing an assign, and then only assign the user_id again, there rest of the data will stay the same.
To fix this problem, we would call the $this->reset() function after a query.
public function query($_query){
$this->query = $_query;
$this->result = #mysql_query($_query, $this->link_id) or die( $_query."<p>".mysql_error($this->link_id) );
$this->reset();
return $this->result;
}
or you could call it in the individual insert or update functions:
public function insert($table){
// .... stuff
$this->query($sql);
$this->reset();
return $this->insert_id();
}
The other possibility is that the original programmer didn't convey his intent to you well enough. He might expect you to call $db->reset() after every query.