PHP Tutorial. Experience and Skills (Part 2)_PHP Tutorial

3. Files are our friends
No matter the size of the website you are developing, you should be aware of the importance of code reuse, whether the code is HTML or PHP code. For example, you must change the footer containing copyright information at least once a year, which is annoying if you have a website with 1,000 pages.

In PHP, there are at least a few functions that can help you achieve code reuse. The functions used depend on the code you are reusing. The main functions are:

* include( ) and include_once()

　* require() and require_once()

　include() function includes and calculates the given file, for example:

include(/ home/me/myfile);

Any code in the include file is executed within the scope of the code where include() appears. You can include it on your own server by using include() and fopen() together. Static files, containing target files on another server.

The function of include_once() is the same as include(). The difference between the two is that it will check whether the code in a file is already included in the existing script. If the code already exists, it will not Include it again.

The require() function replaces itself with the contents of the given file. This replacement process occurs when the PHP engine compiles the code, not during execution. It does not calculate first like include() . The require() function is more used in static elements, while include() is used more in dynamic elements. Similar to include_once(), require_once() will first check whether the given code has been inserted. If the code already exists, it will not be inserted again.

In order to understand its content, I prefer to use the require function in copyright information, static text and other elements that do not contain variables or rely on other executing scripts. For example:

　

　

　 🎜>　[a lot of content]

　
　 // insert copyright

　require(/home/me/mycopyright);

　　? >

　

　

On the other hand, I often use include() at the beginning of the file to control many functions:

　
　//Get the function library

　include(/home/me/myfunctions);

　// do PHP things with my functions ?>

　

　


　[a lot of content]

　

　

　 The next question should be "Where are the include and require files? ?" The simple answer to this question is, "Anywhere in the system." If your code contains database connections with usernames and passwords, you definitely don't put them in the document root. Everyone is open.

The included or required files can be anywhere on the system, as long as they are accessible to users on the system where PHP is running. You can make these files have any suffix, or use no suffix.

It is a common phenomenon to use include() and require() to specify elements in the website, and it will bring you great convenience when you need to upgrade the website.

4. Maintenance of PHP and file system
There are many functions related to the file system in PHP. These functions can not only open files, but also display the contents of the directory, move files and other functions. Many people even use PHP to develop Internet-based file explorers.

Explanation on file paths: In Windows, you can use / and symbols in the path, while in other operating systems only / symbols can be used. For the sake of consistency, we use the / notation uniformly.

The following script example can display a directory list, and the comments have been included in the code:

　
　$dir_name = "/home/me/";

　 /* Create a handle whose value is the result of opening a given directory */

　$ dir = opendir($dir_name);

/* Create a text block to place list elements (file names) */

$file_list = "

";

　/* Use a while statement to read all elements in the opened directory. If the file name is not "." or "..", display the name in the list*/

while ($file_name = readdir($dir)) {

if (($file_name != ".") && ($file_name != "..")) {

$file_list .= "
• $file_name";
  
  　}
  
  　}
  
  　$file_list .= "

";

　/ *Close the open directory and end the PHP module*/

　closedir($dir);

　?>

　

　

　

　
　

　

　

Files in:

　

　

　

　

Okay, we’ve got a directory listing. It should be noted that to read the contents of a file (we will explain this later) or directory, the user on the system where PHP is running must have at least read permissions for the file.

The following is an example of how to copy a file:

　
$original = "/home/me/mydatabasedump";

$copied = "/archive/mydatabasedumo_1010";

　/* Use the copy() function to copy the original file. If the copy is not completed, an error message will be displayed*/

　 @copy($original, $copied) or die("Couldnt copy file .");

　?>

　 This example is a prototype of a file backup system. When this script runs, it copies the file to a different location and saves it. Modify the daemon slightly so that it can be executed at times of day you specify without user intervention.

Assuming you have Lynx installed on your system, you can create a daemon entry to access this file. Accessing this file will run this script and create a copy of the file. The following example will run this at 5 AM Script, then shut down Lynx:

0 5 * * * [username] lynx -dump http://localhost/copyfile.php 1>/dev/null 2>&1

If running It is the CGI version of PHP. You can skip the Lynx part and call the binary file directly:

　0 5 * * * [username] php /path/to/copyfile.php 1>/dev/null 2>&1

5. Rich array functions
PHP 4.0 has added 30 new functions related to the number of groups. Some of the common functions can determine whether an array contains an element. Count elements, add or delete elements in an array, or sort elements in an array.

If you have a large array and you need to find out whether it contains a specific element, you can use in_array(). The following example will display "Not found in this array" because it is looking for Albert in an array named $namesArray, and such an element does not exist in the $namesArray array.

　
　$ lookingFor = "Albert";

if (in_array($lookingFor, $namesArray)) {

echo "Youve found it!";

} else {

echo "Not found in this array!";

　}

?>

If you change the value of $lookingFor to Mary, you will get "You've found it!" message because Mary is an element in the $namesArray array.

If you want to count the number of elements in an array, simply use the count() function:

　
　 $count = count($namesArray); ?>

　 Returned $ The value of count is 7.

You can add elements at the beginning or end of an array. You can also use array_merge() to create a new array containing the elements in two or more arrays. When merging, the order of the elements will be as specified. Sequential arrangement, if the original array was sorted, it needs to be reordered after merging.

We can first use array_push() to add an element at the end of the array:

　
$fruitArray = array(" apple", "orange", "banana", "kiwi", "pear");

　/* Add elements to the array*/

　array_push($fruitArray, "grape", "pineapple", "tomato");

/*Display each element and its serial number*/

while (list($key,$value) = each($fruitArray)) {

echo "$key : $value
";

　}

　?>

Running the above program will get the following results:

0: apple

1: orange

2: banana

3: kiwi

4: pear

5: grape

6: pineapple

7: tomato

If you need to add an element at the beginning of the array, the code is similar to the code above, the only difference is It is necessary to use array_unshift() instead of array_push().

　
　 /* Create an array*/

　$fruitArray = array("apple", "orange", "banana", "kiwi", " pear");

　/* Add elements to the array*/

　array_unshift($fruitArray, "grape", "pineapple", "tomato");

　/ * Display each element and its serial number*/

while (list($key,$value) = each($fruitArray)) {

echo "$key : $value
";

　}

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