8 Tips for PHP and MySQL Development_PHP Tutorial-PHP Tutorial-php.cn

For websites with LAMP architecture, I used to pay more attention to the installation/configuration aspects, and I rarely talked about development because I rarely engaged in development myself. The original text of this article also comes from:
Published on The O'Reilly Network (http://www.oreillynet.com/)
http://www.oreillynet.com/pub/a/onlamp/2002/ 04/04/webdb.html
After reading it, I was quite inspired. Some of the problems encountered in previous development were easily solved. So I translated it and shared it with everyone.
1. The use of arrays in PHP

When operating a database, it is very helpful to use associatively-indexed arrays. Let’s look at a basic number format array. Traversal:
$temp[0] = "richmond";
$temp[1] = "tigers";
$temp[2] = "premiers";
for($x=0 ;$x
{
echo $temp[$x];
echo " ";
}
?>
However, another way to save code is:
$temp = array("richmond", "tigers", "premiers");
foreach ($temp as $element)
echo "$element ";
?>
foreach can also Output text subscript:
$temp = array("club" => "richmond",
"nickname" =>"tigers",
"aim" => "premiers");
foreach ($temp as $key => $value)
echo "$key : $value ";
?>
There are about 50 functions for working with arrays described in the PHP manual
. 2. Add variables to the PHP string
This is very simple:
$temp = "hello"
echo "$temp world";
?>
But it should be noted that although the following example has no error:
$temp = array("one" => 1, "two" => 2);
// Output:: The first element is 1
echo "The first element is $temp[one].";
?>
But if the following echo statement is not enclosed in double quotes, an error will be reported, so it is recommended to use curly braces:
$temp = array("one" => 1, "two" => 2);
echo "The first element is {$temp["one"]}.";
?>
3. Use associative array to access query results

Look at the following example:
$connection = mysql_connect("localhost", "albert", "shhh");
mysql_select_db("winestore", $connection);
$result = mysql_query( "SELECT cust_id, surname,
firstname FROM customer", $connection);
while ($row = mysql_fetch_array($result))
{
echo "ID:t{$row["cust_id "]}n";
echo "Surnamet{$row["surname"]}n";
echo "First name:t{$row["firstname"]}nn";
}
?>
The function mysql_fetch_array() puts a row of the query result into an array, which can be referenced in two ways at the same time. For example, cust_id can be referenced in the following two ways at the same time: $row["cust_id"] or $row[0 ]. Obviously, the former is much more readable than the latter.
In multi-table join query, if two columns have the same name, it is best to use aliases to separate them:
SELECT winery.name AS wname,
region.name AS rname,
FROM winery, region
WHERE winery.region_id = region.region_id;
The references of column names are: $row["wname"] and $row["rname"].
When the table name and column name are specified, only the column name is quoted:
SELECT winery.region_id
FROM winery
The reference of the column name is: $row["region_id"].
The reference of the aggregate function is the reference name:
SELECT count(*)
FROM customer;
The reference of the column name is: $row["count(*)"].
4. Pay attention to common PHP bugs

Common PHP bug correction problems are:
No page rendered by the Web browser when much more is expected
A pop -up dialog stating that the "Document Contains No Data"
A partial page when more is expected
Most of the reasons for these situations are not the logic of the script, but bugs in the HTML or generated by the script HTML bug. For example, if a closing tag like this is missing, the page cannot be refreshed. The solution to this problem is to look at the source code of the HTML.
For complex pages whose reasons cannot be found, you can analyze them through the W3C page validation program http://validator.w3.org/.
If the variable is not defined, or the variable definition is wrong, the program will become weird. For example, the following infinite loop:
for($counter=0; $countermyFunction();
?>
The variable $Counter is increasing, but $counter is always less than 10. This type of error can generally be found by setting a higher error reporting level:
error_reporting(E_ALL);
for($counter=0; $countermyFunction();
?>
5. Use the header() function to process single-part queries

In many web database applications, some functions often allow users to click on a connection and continue to stay. On the current page, I call this kind of work "single part query".
The following is a script called calling.php:
"-//W3C//DTD HTML 4.0 Transitional//EN"
"http://www.w3.org/TR/html4/loose .dtd" >
Click here!
When the user clicks on the link above, action.php is called. The following is the source code of action.php:
// Database function
// Redirect
header("Location: $HTTP_REFERER");
exit;
?>
Here it is Two common mistakes need to be reminded:
After calling the header() function, you must include an exit statement to stop the script, otherwise subsequent scripts may be output before the header is sent. A common error with the
header() function is:
Warning: Cannot add header information - headers already sent... The
header() function can only be called before HTML output, so you need to check php There may be blank lines, spaces, etc. in front.
6. Reload problems and their solutions

When I used to write PHP programs, I often encountered situations where the database would process it once more when the page was refreshed.
Let’s take a look at addcust.php:
$query = "INSERT INTO customer
SET surname = $surname,
firstname = $firstname";
$connection = mysql_connect("localhost", "fred", "shhh");
mysql_select_db("winestore", $connection);
$result = mysql_query($query, $connection);
?>
"-//W3C //DTD HTML 4.0 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd" >
I've inserted the customer for you.
?>
Suppose we use this program with the following connection:
http://www.freelamp.com/addcust.php?surname=Smith&firstname=Fred
If this request is only submitted once, OK, there will be no Problem, but if you refresh multiple times, you will have multiple records inserted.
This problem can be solved through the header() function: Here is the new version of addcust.php:
$query = "INSERT INTO customer
SET surname = $surname,
firstname = $firstname";
$connection = mysql_connect("localhost", "fred", "shhh");
mysql_select_db("winestore", $connection);
$result = mysql_query($query, $connection);
header("Location: cust_receipt.php");
?>
This script redirects the browser to a new page: cust_receipt.php:
"-//W3C//DTD HTML 4.0 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd" >
I've inserted the customer for you.
In this way, the original page continues Refreshing has no side effects.
7. Use lock mechanism skillfully to improve application performance

If we want to run a report urgently, then we can add a write lock to the table to prevent others from reading and writing, so as to increase the processing speed of this table.
8. Use mysql_unbuffered_query() to develop fast scripts

This function can be used to replace the mysql_query() function. The main difference is that mysql_unbuffered_query() returns immediately after executing the query. No need to wait or lock the database.
But the number of rows returned cannot be checked with the mysql_num_rows() function because the size of the output result set is unknown.