Single vs Double quote – when possible use single quote, as double quote strings are processed by PHP.

Accessing data in Arrays – When working with an associative array, PHP operates quickest when the variable array is enclosed in single quotes such as $row[‘thomas’].

Function vs no functions – Everything is passed by reference after PHP 5, which significantly speeds things up, however they are still less efficient than code without functions. If you reuse the code multiple times within the document, functions are a must. If you are only using it once, it is just extra overhead. (This statement is against everything taught in school.)

Extra variables – Try to use as few variables as possible. For example:
$a=time();
$tomorrow=$a + (24*60*60);
is less efficient than
$tomorrow=$time+(24*60*60);

Count () in for loop – There are exceptions to the ‘use as few variables as possible’ rule. The most common is when you have the count function in a conditional loop.

Unset – when you are done using a variable, you can regain the memory by using unset.

Close connections /file handers – Give PHP back the resources when they are not needed.

Cache page if possible.

Lazy way to test

$time = microtime(true);
#
# code to be benchmarked here
#
echo '

Time elapsed: ',microtime(true) - $time, ' seconds';


When you make a call to mysql_query, all of the results get buffered to the server before continuing through the code. If you have a large result set, mysql_unbuffered_query() can speed up your process. Here is what php.net says:

mysql_unbuffered_query() sends the SQL query query to MySQL without automatically fetching and buffering the result rows as mysql_query() does. This saves a considerable amount of memory with SQL queries that produce large result sets, and you can start working on the result set immediately after the first row has been retrieved as you don’t have to wait until the complete SQL query has been performed. To use mysql_unbuffered_query() while multiple database connections are open, you must specify the optional parameter link_identifier to identify which connection you want to use.

You can use this in your code like this: Do not forget to specify the link_identifier if using multiple connections.
$result= mysql_unbuffered_query ("select SQL_CALC_ROWS id as number_of_rows, name from test");
One other note: Note: With mysql_unbuffered_query(), You cannot use mysql_num_rows() but you can use SQL_CALC_ROWS on MySQL to get the total rows without the limit.

$db_host="localhost";
$db_user="test";
$db_password="test";
$db_name="test";

mysql_connect($db_host,$db_user, $db_password) or die(mysql_error());
mysql_select_db($db_name) or die(mysql_error());
$result=mysql_query("select test from test_table");
while($row=mysql_fetch_array($result))
{
    echo $row['test'] , '';
}

error_reporting(E_ALL);
ini_set("display_errors", 1);

Make sure to set this at the top of your document before any code has been outputted by the server.