Use PEAR to buffer PHP programs (ii)

At the end of the program, let's customize an application that synthesizes the overall framework of the PEAR buffering mechanism.








we define a class called Mysql_query_cache, which buffers the query results of a SELECT.





We first define the variables for the class:











<?php


require_once ' cache.php ';





class Mysql_query_cache extends Cache {


var $connection = null;


var $expires = 3600;





var $cursor = 0;


var $result = array ();





function Mysql_query_cache ($container = ' file ',


$container _options = Array (' Cache_dir ' => '. '),


' Filename_prefix ' => ' cache_ '), $expires = 3600)


{


$this->cache ($container, $container _options);


$this->expires = $expires;


}





function _mysql_query_cache () {


if (Is_resource ($this->connection)) {


mysql_close ($this->connection);


}





$this->_cache ();


}


}


?>








before we start, we need some auxiliary functions.





function Connect ($hostname, $username, $password, $database) {


$this->connection = mysql_connect ($hostname, $username, $password) or trigger_error (' Database connection failed! ', e_user_error);





mysql_select_db ($database, $this->connection) or Trigger_error (' Database selection failed! ', e_user_error);


}





function Fetch_row () {


if ($this->cursor < sizeof ($this->result)) {


return $this->result[$this->cursor++];


} else {


return false;


}


}





function Num_rows () {


return sizeof ($this->result);


}


?>








below we see how buffer:





<?php


function query ($query) {


if (stristr ($query, ' SELECT ')) {


//Compute the buffer tag of the query


$cache _id = MD5 ($query);





//Query buffering


$this->result = $this->get ($cache _id, ' Mysql_query_cache ');





if ($this->result = = NULL) {


//buffering loss


$this->cursor = 0;


$this->result = Array ();





if (Is_resource ($this->connection)) {


//Use Mysql_unbuffered_query ()
as far as possible




if (function_exists (' mysql_unbuffered_query ')) {$result = Mysql_unbuffered_query ($query, $this->connection);


} else {$result = mysql_query ($query, $this->connection);


}





//Remove all query results


while ($row = Mysql_fetch_assoc ($result)) {$this->result[] = $row;


}





//Release MySQL result resource


mysql_free_result ($result);


Buffer the results


$this->save ($cache _id, $this->result, $this->expires, ' Mysql_query_cache ');


}


}


} else {


//No query results, no buffering required


return mysql_query ($query, $this->connection);


}


}


?>








Example 3: Using the MySQL query buffer





<?php require_once ' mysql_query_cache.php ';





$cache = new Mysql_query_cache ();


$cache->connect (' hostname ', ' username ', ' password ', ' database ');


$cache->query (' SELECT * from table ');





while ($row = $cache->fetch_row ()) {


echo ' <p> ';


Print_r ($row);


echo ' </p> ';


}


?>


< full finished >