The original text of this article is reproduced from: http://blog.csdn.net/guoguo1980/archive/2006/08/24/1112768.aspx
The author of this article: guoguo1980
Article summary :
When talking about web search engines, most people will think of Yahoo. Indeed, Yahoo created an era of Internet search. However, the technology Yahoo currently uses to search the web was not originally developed by the company. In August 2000, Yahoo adopted technology from Google (www.Google.com), a venture company founded by Stanford University students. The reason is very simple. Google's search engine can search for the required information faster and more accurately than the technology previously used by Yahoo.
It is probably impossible for us to design and develop a powerful and efficient search engine and database ourselves in a short period of time in terms of technology and funds. However, since Yahoo is using others technology, then can we also use other people’s ready-made search engine websites?
Analysis of programming ideas
We can imagine this: simulate a query, issue a search command in a corresponding format to a search engine website, then return the search results, and analyze the HTML code of the results , strip off redundant characters and codes, and finally display it in our own website page in the required format.
In this way, the key to the problem is that we need to select a search information that is accurate (so that our search will be more meaningful) and fast (because we need extra time to analyze the search results and display them) , a search website with concise search results (convenient for HTML source code analysis and stripping). Due to various excellent features of the new generation search engine Google, here we choose it as an example to see how to use PHP to implement background processing of Google (www.Google.com) search and front-end personalized display process.
Let’s first take a look at the composition of Google’s query commands. Enter the www.Google.com website, enter "abcd" in the query bar, click the query button, we can find that the browser's address bar changes to: http://www. Google.com/search?q=abcd&btnG=Google%CB%D1%CB%F7&hl=zh-CN&lr=, it can be seen that Google passes the query parameters and submits the query command through the get method of the form. We can use the file() function in PHP to simulate this query process.
Understand the File() function
Syntax: array file(string filename);
The return value is an array, and all files are read into the array variable. The file here can be local or remote. The remote file must indicate the protocol used. For example: result=file(“http://www.Google.com/search?q=abcd&btnG=Google%CB%D1%CB%F7&hl=zh-CN&lr=” ), this statement will simulate the process of querying the word "abcd" on Google, and transfer the search results back to the array variable result in the form of elements per row. Because the file read here is remote, the protocol name "http://" cannot be missing.
If you want the user to enter search characters for any search, we can make an input text box and submit button, and replace the searched character "abcd" above with a variable:
echo
; //For a form without parameters, the default submission method is get, submitted to itself
echo; //Construct a text input box
echo; //Construct a submit query button
echo
;
if (isset( $keywords)) //After submission, PHP will generate the variable kwywords, which requires the following program to run after submission
{
urlencode( $keywords) ; //URL encode the user input
result=file(http://www.Google.com/search?q=. $keywords.&btnG=Google%CB%D1%CB%F7&hl=zh-CN&lr =);
//Replace variables in the query statement and save the query results in the array variable result
$result_string=join(, result); //Merge the array $result into a string, each array element Use spaces to paste
... //further processing
}
?>
Note: The above can be used file_get_contents() function to implement, $result_string=file_get_contents(“http://....")
The above program can already query based on user input and synthesize the returned result into a string variable $result_string. Please note that you must use the urlencode() function to URL-encode the user input so that the input Chinese characters, spaces, and other special characters can be queried normally. This also simulates Google's query commands as realistically as possible to ensure the search results are accurate. Correctness.
Analysis of Google
For ease of understanding, let’s assume that what we really need is: the title of the search results. URL and introduction, etc. This is a simple and typical requirement. In this way, all we have to do is: remove the header and footer of Google search results, including a Google logo, input box for re-search, search result description, etc., and strip the original HTML from the remaining search result items. Format tag, replace it with the format we want.
To do this, we must carefully analyze the HTML source code of Google search results and find the patterns. It is not difficult to find that the text of Google search results is always included between the first
tag and the penultimate
tag of the source code, and the penultimate
The mark is followed by the table character, and this combination "
All the following procedures are continued in the "further processing" of the above program.
result_string = strstr( result_string,
); //Get the string after result_string starting from the first
to remove the Google header
position= strpos( result_string,
table symbol Position
result_string= substr(result_string,0, position);//Intercept the string before the first
table symbol to remove the footnote
Application and Implementation
OK, now that we have obtained the useful HTML source code backbone, the remaining problem is how to display this content autonomously. Let’s analyze these search result entries and find that there are also very regular uses between each entry
Separate, that is, each entry is divided into a paragraph. According to this feature, we use the explode() function to cut each entry:
Syntax: explode(string separator, string string);
Return An array, each small string divided by separator is saved in the array
So:
result_array=explode(
, result_string); //Use string
. >
Cut the results
We get an array result_array, where each element is a search result entry. All we have to do is study each entry and its HTML display format code, and then. Just replace as required. Use a loop to process each entry in result_array ( i=0; i {
... //process each entry
}
For each entry, we can easily find some characteristics: each entry is composed of title, abstract, introduction, category, URL, etc. Each part is line-wrapped, that is, it contains the
tag, so it is divided again: (below The handler is placed in the loop above)
every_item=explode(
, result_array[ i]);
In this way we get an array every_item, where every_item[0] is the title, every_item[ 1] and every_item[2] are two lines of summary. If the headers of every_item[3], every_item[4], etc. contain "Introduction:", " Category:" character, it is an introduction or category (because some result entries do not have this item). If the header contains "", it must be the URL. We often use regular expressions for this kind of comparison. (omitted), it is also very convenient if you want to replace it. For example, $every_item[0] containing the title has a link itself. We want to modify this link attribute so that it opens the link in a new window:
echo eregi_replace( {
... //Process each item except the first item in each entry (the first item is the title, which has been displayed)
... //More format modifications
}
In this way, the link attribute is modified, and many other display format modifications, stripping, and replacements can be completed using regular replacement eregi_replace().
At this point we have obtained each item of each search item, and can modify the format of each item at will, and even put a beautiful table on it. However, a good program should be able to adapt to various operating environments, and here is no exception. In fact, we have only discussed a framework method for HTML stripping of search results. To really do it perfectly, there are many things to consider, such as It displays the total number of search results, how many pages it is divided into, etc. It can even remove the "category", "introduction" and other codes related to Google, so that customers cannot see the original website at all. However, we can all extract these contents and requirements by analyzing HTML. Now everyone can do it themselves and build a highly personalized search engine.

php把负数转为正整数的方法:1、使用abs()函数将负数转为正数,使用intval()函数对正数取整,转为正整数,语法“intval(abs($number))”;2、利用“~”位运算符将负数取反加一,语法“~$number + 1”。

实现方法:1、使用“sleep(延迟秒数)”语句,可延迟执行函数若干秒;2、使用“time_nanosleep(延迟秒数,延迟纳秒数)”语句,可延迟执行函数若干秒和纳秒;3、使用“time_sleep_until(time()+7)”语句。

php除以100保留两位小数的方法:1、利用“/”运算符进行除法运算,语法“数值 / 100”;2、使用“number_format(除法结果, 2)”或“sprintf("%.2f",除法结果)”语句进行四舍五入的处理值,并保留两位小数。

判断方法:1、使用“strtotime("年-月-日")”语句将给定的年月日转换为时间戳格式;2、用“date("z",时间戳)+1”语句计算指定时间戳是一年的第几天。date()返回的天数是从0开始计算的,因此真实天数需要在此基础上加1。

php判断有没有小数点的方法:1、使用“strpos(数字字符串,'.')”语法,如果返回小数点在字符串中第一次出现的位置,则有小数点;2、使用“strrpos(数字字符串,'.')”语句,如果返回小数点在字符串中最后一次出现的位置,则有。

php字符串有下标。在PHP中,下标不仅可以应用于数组和对象,还可应用于字符串,利用字符串的下标和中括号“[]”可以访问指定索引位置的字符,并对该字符进行读写,语法“字符串名[下标值]”;字符串的下标值(索引值)只能是整数类型,起始值为0。

方法:1、用“str_replace(" ","其他字符",$str)”语句,可将nbsp符替换为其他字符;2、用“preg_replace("/(\s|\ \;||\xc2\xa0)/","其他字符",$str)”语句。

在php中,可以使用substr()函数来读取字符串后几个字符,只需要将该函数的第二个参数设置为负值,第三个参数省略即可;语法为“substr(字符串,-n)”,表示读取从字符串结尾处向前数第n个字符开始,直到字符串结尾的全部字符。


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