Summary of 8 Tips for PHP and MySQL Development_PHP Tutorial

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 array traversal in digital format:

Copy code The code is as follows:

$temp[0] = "richmond";
$temp [1] = "tigers";
$temp[2] = "premiers";

for($x=0;$x{
echo $temp[$x];
echo " ";
}
?>

However, another way to save code is:

Copy code The code is as follows:

$temp = array("richmond", "tigers", "premiers");
foreach ($temp as $element)
echo "$element ";
?>

foreach can also output text subscripts:

Copy code The code is as follows:

$temp = array("club" => "richmond ",
"nickname" =>"tigers",
"aim" => "premiers");

foreach ($temp as $key => $value)
echo "$key : $value ";
?>

About 50 functions for working with arrays are described in the PHP manual.
2. Add variables to the PHP string
This is very simple:

Copy the code The code is as follows:

$temp = "hello"
echo "$temp world";
?>

But it needs to be explained Yes, although there is no error in the following example:

Copy the code The code is as follows:

$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:

Copy the code The code is as follows:

$temp = array("one" => 1, "two" => 2);
echo "The first element is {$temp["one"]}.";
?>

3. Use associative array to access query results
Look at the example below:

Copy the code The code is as follows:

$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 bugs in the HTML generated by the script. . For example, if closing tags like , , are 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:

Copy code The code is as follows:

for($counter= 0; $counter<10; $Counter++)
myFunction();
?>

The variable $Counter is increasing, and $counter is always less than 10. This type of error can generally be found by setting a higher error reporting level:

Copy code The code is as follows:

< ;?php
error_reporting(E_ALL);

for($counter=0; $counter<10; $Counter++)
myFunction();
?>

5. Use the header() function to process single-part queries
In many web database applications, some functions often allow users to continue to stay on the current page after clicking a connection. This kind of work I call it "single part query".
The following is a script called calling.php:

Copy the code The code is as follows:

Click here!< /a>

When the user clicks the above link, action.php is called. The following is the source code of action.php:

Copy the code The code is as follows:

// Database Function
// Redirect
header("Location: $HTTP_REFERER");
exit;
?>

There are two common mistakes to be reminded of here Below:
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 in the

header() function is:
Warning: Cannot add header information - headers already sent... The
header() function can only be called before HTML output, so you You need to check for empty lines, spaces, etc. that may exist in front of php.
6. Reload problems and their solutions
When I used to write PHP programs, I often encountered situations where the database would process it more than once when the page was refreshed.
Let’s take a look at addcust.php:

Copy the code The code is as follows:

$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. ... &firstname=Fred
If this request is submitted only once, OK, there will be no problem, but if you refresh it multiple times, you will insert multiple records.
This problem can be solved through the header() function: The following is the new version of addcust.php:

Copy the code The code is as follows:

$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);
he

header("Location: cust_receipt.php");
?>

This script redirects the browser to a new page: cust_receipt.php:

Copy the code The code is as follows:

I've inserted the customer for you.

In this way, the original page will not continue to refresh. Side effects.
7. Cleverly use the lock mechanism 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 to improve the performance of the table. processing speed.
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, without waiting. 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.

http://www.bkjia.com/PHPjc/322576.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/322576.htmlTechArticle1. The use of arrays in PHP When operating databases, it is very helpful to use associatively-indexed arrays. , below we look at a basic array traversal in digital format:...