Chapter II Storage and retrieval of data (2)

Focus:

• Know when to finish reading files: feof () function
• Reads one row of data at a time: fgets (), FGETSS (), fgetcsv () functions
• Read entire file: ReadFile (), Fpassthru (), file () function
• Read one character: Fgetc () function
• Read any length: Fread () function
• To see if a file exists: File_exists () function
• Determine file Size: FileSize () function
• Delete a file: Unlink () function
• Locate in File: Rewind (), fseek (), Ftell () function
• File Lock: Flock () function (previously spoken)

An example of reading a file first: program manifest 2-3 vieworder.php--the employee interface used to view the order file

<?PHP//Create short variable name$DOCUMENT _root=$_server[' Document_root '];?>s Auto parts-customer orders</title>' s Auto partsPHP//Open the file (orders.txt); "RB" means "only can read"@$fp=fopen("$DOCUMENT _root/.. /orders.txt ", ' RB '); //lock file for reading    Flock($fp,lock_sh); //judge the file is full or not    if(!$fp){        Echo"<p><strong>no orders pending. Please try again later.</strong></p> "; Exit; }    //judge when the file go to the end     while(!feof($fp)){        er=fgets($fp, 999); //Read one line of content from the this file each time , it would stop when counter a "\ n" or "EOF" or 998B        Echo er." <br/> "; }    Echo"Final position of the file pointer is:". (Ftell($fp)); Echo"<br/>"; Rewind($fp); Echo"After rewind, the position is:". (Ftell($fp)); Echo"<br/>"; //Release the file    Flock($fp,Lock_un); fclose($fp); ?></body>View Code
Then I go through the line analysis:
    while (!feof ($fp)) {        er = fgets ($fp, 999);        Read one line of content from the this file each time, it would stop when counter a "\ n" or "EOF" or 998B        echo er. " <br/> ";    }
This uses the Fgets () function, which reads one row of data at a time, and the feof () function, which functions as "judging when to read a file".
First, the meaning of this code: the use of a while loop, when the file pointer FP does not reach the end of the file, each time a row is read, when the file pointer reads "\ n"/"EOF"/998b, a line break is printed on the vieworder.php interface.
A little tip:

 
 

  
  
 
   
 
    
 
     
 
      
 
       
The Web browser does not represent spaces, such as Sia, so we'd better replace the line terminator in the text with the newline character in HTML <br/>.
 
       
999: Here is the maximum readable length for the specified length (we ourselves as per the actual conditions) minus 1B, i.e. 998B.
 
      
 
    
 
   
Feof () function: Test If the file pointer is at the end of the file--bool feof (Resource $handle)
 
  
 
 
Handle: Represents a file pointer, in this case the handle is "$fp".
If the file pointer points to the end of the file, the feof () function returns True.
Foef ==file End of File.

 
 

  
  
 
   
Reads one row of data at a time: fgets (), FGETSS (), fgetcsv () functions 
    
 
     
 
      
 
       
Fgets (): reads a line of content from the file pointer every time--string fgets (Resource $handle [, int $length])
 
      
 
    
 
  
 
 
Handle: The file pointer is required and must point to a file that was successfully opened by fopen () or Fsockopen () (and not yet closed by fclose ())
Length: Reads a row from the file pointed to by handle and returns a string of up to length-1 bytes in length. Encounters a newline character (included in the return value), EOF, or
The length-1 byte has been read and stopped (see what happens first). If length is not specified,   The default is 1 K, or 1024 bytes. 

 
 

  
  
 
   
 
    
 
     
 
      
 
       
FGETSS (): Reads a row from the file pointer and filters out the HTML tag--string fgets (Resource $handle [, int $length [, String $allowable _tags]])
 
      
 
    
 
  
 
 
Allowable_tags: Optional third parameter specifies which tags are not removed

 
 

  
  
 
   
 
    
 
     
 
      
Fgetcsv (): reads a line from the file pointer and resolves the CSV field--ArrayFgetcsv(Resource$handle[, Int$length= 0[, string  $delimiter   = ', '  [,  string  $enclosure   = ' "'   [, string  $escape   = ' \ \ ' &NBSP;]]])     
 
     
 
   
 
 
Delimiter: Set field delimiter (only one character allowed)
Enclosure: Set field wrapping character (only one characters allowed)
Escape: Set escape character (only one character allowed), default is a backslash
Returns an indexed array containing the Read fields
　
    echo "Final position of the file pointer is:". (Ftell ($FP));    echo "<br/>";    Rewind ($FP);    echo "After rewind, the position is:". (Ftell ($FP));    echo "<br/>";
The Ftell () function and the rewind () function, which functions as "Locating in Files" are used here,
First of all, the meaning of this code: print out the last position of the file pointer----wrap--Reset the file pointer to the beginning of the file--after the print reset, the position of the pointer--newline

 
 

  
  
Locate in File: Rewind (), fseek (), Ftell () function 
   
 
    
 
     
 
      

      
Rewind (): Rewind the position of the file pointer (the file location that will be handle is set to the beginning of the file stream)--bool Rewind (Resource $handle)
 
      
Fseek (): Locating in the file pointer--Int   fseek    (  resource  $handle  Span class= "Apple-converted-space" > , < Span class= "type" >int  $offset   [,  int  $whence   = seek_set  ])                
 
     
 
   
 
 
 < Span class= "Apple-converted-space" >  < Span class= "Apple-converted-space" > offest: Offset. To move to the position before the end of the file, you need to pass a negative value to offset and set whence to Seek_end.  
 < Span class= "Apple-converted-space" >  < Span class= "Apple-converted-space" > whence:                      
 < Span class= "Apple-converted-space" >  < Span class= "Apple-converted-space" >" 1 "seek_set-Set position equals offset byte        / span>             
 < Span class= "Apple-converted-space" >  < Span class= "Apple-converted-space" >" 2 "seek_cur-set position for current position plus offset        
 < Span class= "Apple-converted-space" >  < Span class= "Apple-converted-space" >" 3 "seek_end-set location for end of file plus offest         /span>             

 
 

  
  
 
   
 
    
 
     
 
      
 < Span class= "Apple-converted-space" >ftell (): Returns the position of the file pointer read/write--int < Span class= "methodname" >  ftell    ( resource   $handle   )            　　　　　　　　　　　
 
     
 
   
 
 
　　　　　　　　　　　　
Chapter II Storage and retrieval of data (2)