Summary of common methods for reading files in PHP

This article mainly introduces a summary of common methods of reading files in PHP. Interested friends can refer to it. I hope it will be helpful to everyone.

1.fread

string fread ( int $handle , int $length )

fread() points from handle Read up to length bytes from the file. This function is called after reading up to length bytes, or when EOF is reached, or (for network streams) when a packet is available, or (after opening a user space stream) 8192 bytes have been read. Will stop reading the file, depending on which condition is encountered first.

fread() returns the string read, or FALSE if an error occurs.

<?php
  $filename = "/usr/local/something.txt";
  $handle = fopen($filename, "r");//读取二进制文件时，需要将第二个参数设置成&#39;rb&#39;
  
  //通过filesize获得文件大小，将整个文件一下子读到一个字符串中
  $contents = fread($handle, filesize ($filename));
  fclose($handle);
?>

If the file to be read is not a local ordinary file, but a remote file or stream file, this method cannot be used, because filesize cannot obtain the size of these files. At this time, you need to use the return value of feof() or fread() to determine whether the end of the file has been read.

For example:

<?php
  $handle = fopen(&#39;http://www.baidu.com&#39;, &#39;r&#39;);
  $content = &#39;&#39;;
  while(!feof($handle)){
    $content .= fread($handle, 8080);
  }
  echo $content;
  fclose($handle);
?>

or:

<?php
  $handle = fopen(&#39;http://www.baidu.com&#39;, &#39;r&#39;);
  $content = &#39;&#39;;
  while(false != ($a = fread($handle, 8080))){//返回false表示已经读取到文件末尾
    $content .= $a;
  }
  echo $content;
  fclose($handle);
?>

2.fgets

string fgets ( int $ handle [, int $length ] )

fgets() reads a line from the file pointed to by handle and returns a string with a length of at most length - 1 bytes. Stops when a newline character (included in the return value), EOF, or length - 1 bytes has been read (whichever occurs first). If length is not specified, it defaults to 1K, or 1024 bytes.

<?php
  $handle = fopen(&#39;./file.txt&#39;, &#39;r&#39;);
  while(!feof($handle)){
    echo fgets($handle, 1024);
  }
  fclose($handle);
?>

Note: The length parameter is optional as of PHP 4.2.0, if omitted, the length of the line is assumed to be 1024. Starting with PHP 4.3, omitting length will continue reading from the stream until the end of the line. If most of the lines in the file are larger than 8KB, specifying the maximum line length in the script is more efficient in utilizing resources. Starting with PHP 4.3 this function is safe for use with binary files. Earlier versions don't.

3.fgetss

string fgetss ( resource $handle [, int $length [, string $allowable_tags ]] )

Same function as fgets, but fgetss will try to remove any HTML and PHP tags from the read text. You can use the optional third parameter to specify which tags are not to be removed.

<?php
  $handle = fopen(&#39;./file.txt&#39;, &#39;r&#39;);
  while(!feof($handle)){
    echo fgetss($handle, 1024, &#39;<br>&#39;);
  }
  fclose($handle);
?>

4.file

<?php
  $a = file(&#39;./file.txt&#39;);
  foreach($a as $line => $content){
    echo &#39;line &#39;.($line + 1).&#39;:&#39;.$content;
  }
?>

5.readfile##int readfile ( string $filename [, bool $use_include_path [, resource $context ]] )

Read a file and write it to the output buffer. Returns the number of bytes read from the file. Returns FALSE on error and displays an error message unless called as @readfile().

<?php
  $size = readfile(&#39;./file.txt&#39;);
  echo $size;
?>

6.file_get_contentsstring file_get_contents ( string $filename [, bool $use_include_path [, resource $context [, int $offset [ , int $maxlen ]]]] )

Read the file into a string. The third parameter $context can be used to set some parameters, such as setting timeout when accessing remote files, etc.

In addition, file_get_contents has much better performance than the above functions, so file_get_contents should be given priority. But readfile seems to have better performance than file_get_contents (?), because it does not need to call fopen.

<?php 
  $ctx = stream_context_create(array( 
    &#39;http&#39; => array( 
      &#39;timeout&#39; => 1  //设置超时
      ) 
    ) 
  ); 
  echo file_get_contents("http://www.baidu.com/", 0, $ctx); 
?>

7.fpassthruint fpassthru (resource $handle)

Change the given file pointer from the current The position is read to EOF and the result is written to the output buffer.

<?php 
  header("Content-Type:text/html;charset=utf-8"); 
  $handle = fopen(&#39;./test2.php&#39;, &#39;r&#39;);
  fseek($handle, 1024);//将指针定位到1024字节处
  fpassthru($handle);
?>

8.parse_ini_filearray parse_ini_file ( string $filename [, bool $process_sections ] )

parse_ini_file() Loads an ini file specified by filename and returns its settings as an associative array. If you set the final process_sections parameter to TRUE, you will get a multidimensional array containing the name and settings of each section in the configuration file. The default value for process_sections is FALSE.

Note: 1. If the value in the ini file contains any non-alphanumeric characters, it needs to be enclosed in double quotes (").

2. Some reserved words cannot be used as key names in ini files, including: null, yes, no, true and false. The values ​​​​are null, no and false are equivalent to "", the value Equivalent to "1" for yes and true. The characters {}|&~![()" also cannot be used anywhere in key names, and these characters have special meaning in option values.

test.ini file content:

; This is a sample configuration file
; Comments start with ';', as in php.ini

[first_section]
one = 1
five = 5
animal = BIRD

[second_section]
path = "/usr/local/bin"
URL = "http://www.example.com/~username

test.php content:

<?php 
  $config = parse_ini_file(&#39;./test.ini&#39;, ture);
  print_r($config);
?>

Output content:

Array
(
  [first_section] => Array
    (
      [one] => 1
      [five] => 5
      [animal] => BIRD
    )

  [second_section] => Array
    (
      [path] => /usr/local/bin
      [URL] => http://www.example.com/~username
    )

)

A few notes Matters: 1. It is encouraged to use the b flag when processing binary files, even if the system does not require it, which makes the script more portable.

2. The allow_url_fopen option activates the URL form of the fopen encapsulation protocol so that URL objects such as files can be accessed. The default encapsulation protocol provides access to remote files using the ftp and http protocols. Some extension libraries such as zlib may register more encapsulation protocols. For security reasons, this option can only be set in php.ini.

3. If you want to open a URL with special characters (for example, spaces), you need to use urlencode() for URL encoding.

Summary: The above is the entire content of this article, I hope it will be helpful to everyone's study.

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