Seven PHP Application Tips_PHP Tutorial

PHP (Hypertext Preprocessor) is an HTML embedded language and is currently a popular web programming language. It supports a wide variety of back-end databases, covering almost all current database systems. At the same time, it includes functions such as mathematical operations, time processing, file system, string processing, and itinerary processing that are common in general languages. In addition, it is a free system, making the cost-benefit ratio almost infinite.
The following are some tips I have summarized when using PHP to build a website, and I will share them with you.
1. Determine whether a certain function is supported
Since in PHP we can flexibly increase or decrease the modules supported by PHP, sometimes we always determine a module first before using PHP Whether it is loaded, for example, to see if the GD graphics module is supported, you can use the following code:
if(!function_exists('imagecreate')) {
die('This host does not currently support GD graphics Module');
}
?>
In the same way, we can use similar code to test whether MSSQL, OCI and other modules are supported.
2. Change the URL in the string to a hyperlink
When submitting a form on a web page, some URLs, such as personal homepage and other information, often appear in the submitted description text. If they are automatically redirected when displayed, It will be a very pleasant thing to create a hyperlink, just like a hyperlink automatically appears when editing a document with WORD. The following code implements its function very well.
$string = "Connect to Ccidnet http://www.ccidnet.com site";
//Note: There needs to be a space or a carriage return after the connection.
$string = eregi_replace("http://([^ ,rn]*)","＜a href= tarrget=_blank＞＜/a＞",$string);
$string = eregi_replace( "ftp://([^ ,rn]*)","＜a href= target=_blank＞＜/a＞",$string);
print $string;
?>
3 , Use PHP to process multiple checkboxes with the same name
If there are multiple checkboxes with the same name in a form, there will only be one value when submitted to PHP, instead of a string of comma-separated values ​​like ASP. The solution is to use arrays. Add [] after the name of the check box, for example: changed to: . This way php will get an array called pp. In the submitted form, first use Count(pp) to determine the number of arrays, that is, the number of selected items, and then process the arrays separately.
The same principle is also applicable to multi-select problems in drop-down boxes.
4. Use static to realize the color display of the table in alternate rows
We use PHP to query the data from the database and output the results to the browser. If the result has many rows, if the bgcolor (background color) of the table is all single If it is too colorful, viewers will feel uncomfortable. So how to make the colors of each row of the table different? Please look at the following code:
function getcolor()
{
static $colorvalue;//Define a static variable
if($colorvalue=="#eeeeee")
$colorvalue=" #F5F5F5";
else $colorvalue="#eeeeee";
return($colorvalue);
}
print("＜table border=1＞n");//The following output is 10 Line
for($i=0;$i{
$bcolor=getcolor();//Change the background color
print("＜tr bgcolor=$bcolor ＞n");
print("＜td＞$i＜/td＞n");
print("＜/tr＞");
}
print("＜/table ＞n");
?>
Explanation:
A static variable static $colorvalue is defined in this program, which means that after the function call ends, this variable $colorvalue still retains its value and does not disappear. When the getcolor() function is called again, the value of the variable $colorvalue is the value of $colorvalue at the end of the last function call.
5. Ways to avoid repeated references in php
As we all know, in C language, we can use #define to define a MACRO name, and determine whether the header file is referenced by checking whether the MACRO name is defined. . There is the same problem in PHP, for example: A refers to B, C, B refers to C. If no measures are taken, C will be quoted twice. This may cause some strange problems. Solution: Define a global variable and solve this problem by checking whether the variable is defined. The method is very simple, similar to C. It’s just that I recommend using the naming rule of ['user_packages'] ['headfilename'] for this global variable.
if (!empty($GLOBALS['FOODTAILS']['GLOBALDEFINE'])) return;
$GLOBALS['FOODTAILS']['GLOBALDEFINE'] = true;
class FOODTAILS {.. .
};
?>
In addition, try to use require_once "headfiles.php"; in the main program to avoid repeated references.
6. How to avoid repeated submission of forms
When we are building websites, we often worry about some spam articles. Sometimes, due to network conditions and other reasons, users do not know whether the submission is successful and will submit the same form again, which results in repeated submission of the form. There is an easy way to avoid duplicate submissions of the same form. First, define a session variable to save the submission sequence number of a form. Here I define it as "$userLastAction".Then add a hidden variable to the form and set the value to $userLastAction+1: > Finally, determine whether the form has been submitted before processing the submission.
if($lastAction>$userLastAction){
$userLastAction++; // Increment the sequence number by 1
// Process form data
}
?>
The main principle of this technique is Users are not allowed to resubmit after going back, which means that they are not allowed to modify and resubmit after going back, but the Ctrl-C/Ctrl-V irrigation method cannot be avoided.
7. Backfilling of download times of downloaded files
When we download software, we often see the download statistics of this software, and these statistics make it convenient for website administrators to analyze the popularity of the software. The implementation principle is: store the unique identification and download number of the software in the back-end database. When the user downloads the software, the number of downloads of the corresponding software is first updated, that is, the number of downloads is increased by 1, and then the download is officially started on the download file. Please look at the implementation code below:
a. First create a data table download (using MySql for the backend)
The download table contains the following two fields:
id The unique identifier of the downloaded file
downnum Number of downloads, the default value is 0
b, implementation
Assume that it has been taken out from the database: description file name Wubi font; download file name: wbzx.zip; identification number id value is 2
Generated after processing The hyperlink code is:

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