PHP file reading and writing tutorial: Detailed introduction to the basic methods and processes of reading and writing

PHP file reading and writing tutorial: Detailed introduction to the basic methods and processes of reading and writing

Introduction:
When developing Web applications, the file Read and write operations are very basic and common operations. PHP provides a series of methods and functions to implement file reading and writing operations, and is very simple and easy to use. This tutorial will introduce in detail the basic methods and processes of reading and writing files in PHP, and give code examples.

1. Reading files

1. Open the file
   Before starting to read the file, you first need to open the file. A file can be opened through the fopen() function, which accepts two parameters: the file path and name, and the mode for opening the file.

$file = fopen("test.txt", "r");

In the above example, we opened the file named test.txt and used the "r" mode, which means opening the file in read-only mode.

2. Read file content
   After opening the file, we can use various methods to read the file content. Common methods are:

• fgets() function: Read the file content line by line until the end of the file or the specified number of lines.

while (!feof($file)) {
    $line = fgets($file);
    echo $line . "<br>";
}

• fread() function: Read the file content of the specified length.

$content = fread($file, filesize("test.txt"));
echo $content;

3. Close the file
   After the file reading operation is completed, the file should be closed in time to release system resources. Files can be closed using the fclose() function.

fclose($file);

2. Writing files

1. Open the file
   Before starting to write the file, you also need to open the file first. You can open a file through the fopen() function and specify the mode for opening the file.

$file = fopen("test.txt", "w");

In the above example, we opened the file named test.txt and used the "w" mode, which means opening the file for writing. If the file does not exist, a new file is created. If the file already exists, the file contents will be cleared.

2. Write file content
   After opening the file, we can use the fputs() function or fwrite() function to write the file content.

• Use fputs() function:

fputs($file, "Hello, World!");

• Use fwrite() function:

fwrite($file, "Hello, World!");

3. Close the file
   After the file writing operation is completed, the file should also be closed to release system resources. Files can be closed using the fclose() function.

fclose($file);

3. Complete example
The following is a complete example that demonstrates how to read the contents of a file and write the contents to another file.

// 打开待读取的文件
$readFile = fopen("source.txt", "r");

// 打开待写入的文件
$writeFile = fopen("target.txt", "w");

// 逐行读取文件内容并写入到目标文件
while (!feof($readFile)) {
    $line = fgets($readFile);
    fputs($writeFile, $line);
}

// 关闭文件
fclose($readFile);
fclose($writeFile);

Summary:
This tutorial introduces in detail the basic methods and processes of reading and writing PHP files. When reading a file, you need to open the file first, and then choose an appropriate method to read the file content. When writing a file, you also need to open the file first, and then choose an appropriate method to write the file content. Finally, the file should be closed promptly to release system resources. I hope this tutorial is helpful to you and can be applied flexibly in actual development.

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