Introduction to PHP functions—fgets(): Read a line from a file

PHP function introduction—fgets(): Read a line from a file

In PHP, reading a file is a very common operation. The fgets() function can help us read data from the file line by line. This function is very useful especially when we need to process large text files. This article will introduce the usage of the fgets() function and provide some code examples to help readers better understand the function and usage of this function.

The basic syntax of the fgets() function is as follows:
string fgets (resource $handle, int $length);

Parameter analysis:

• $handle : A file resource, a resource opened and returned by the fopen() function.
• $length: Optional parameter, specifying the maximum number of bytes to read from the file. Default is 1024 bytes.

Example Code 1: Basic Usage
Suppose we have a text file example.txt with the following content:

Lorem ipsum dolor sit amet,
consectetur adipiscing elit,
sed do eiusmod tempor incididunt
ut labore et dolore magna aliqua.

We want to read each line in it and It is displayed on the page, and the code is as follows:

$handle = fopen("example.txt", "r");

if ($handle) {
    while (($line = fgets($handle)) !== false) {
        echo $line . "<br>";
    }
    fclose($handle);
} else {
    echo "无法打开文件";
}

The program first uses the fopen() function to open the example.txt file, and stores the returned file resource in the $handle variable. Then, in a while loop, use the fgets() function to read one line at a time, assign it to the $line variable, and then output it to the page. Finally, use the fclose() function to close the file.

Execute the above code, the output result is as follows:

Lorem ipsum dolor sit amet,
consectetur adipiscing elit,
sed do eiusmod tempor incididunt
ut labore et dolore magna aliqua.

Sample code 2: Limit the number of bytes read
In some cases, we may only need to read the the first few bytes, or just need to read a fixed number of bytes per line. The second parameter $length of the fgets() function allows us to limit the number of bytes read. For example, we only read the first 10 bytes of each line, the code is as follows:

$handle = fopen("example.txt", "r");

if ($handle) {
    while (($line = fgets($handle, 10)) !== false) {
        echo $line . "<br>";
    }
    fclose($handle);
} else {
    echo "无法打开文件";
}

This code adds the second parameter 10 to the fgets() function call, which means that only 10 bytes are read each time byte. The execution results are as follows:

Lorem ipsu
consectetu
sed do eiu
ut labore 

Sample code 3: Read and process data line by line
In addition to outputting it directly to the page, we can also further process the data of each line. For example, to count the number of characters in each line in a file and store the results in an array, the code is as follows:

$handle = fopen("example.txt", "r");
$result = [];

if ($handle) {
    while (($line = fgets($handle)) !== false) {
        $lineLength = strlen($line);
        $result[] = $lineLength;
    }
    fclose($handle);
} else {
    echo "无法打开文件";
}

print_r($result);

This code uses the strlen() function to calculate the number of characters in each line in each loop, and Store the results in the $result array. Finally, use the print_r() function to output the contents of the array. The execution results are as follows:

Array
(
    [0] => 28
    [1] => 28
    [2] => 30
    [3] => 24
)

Summary
The fgets() function is a very useful function that can help us read data line by line from the file. It's very simple to use and the basic syntax is easy to understand. We can use this function to read each line of the file and perform further processing, such as outputting it to the page, counting the number of characters, etc. By mastering and flexibly using the fgets() function, we can process large text files more conveniently.

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