Summary of some FAQs about operating files in PHP_PHP Tutorial-PHP Tutorial-php.cn

Summary of some FAQs about operating files in PHP_PHP Tutorial

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Release： 2016-07-21 15:48:22

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Q: How to create a new file?
Answer: 1. Use fopen("File name to be created", "Parameter"), the parameters can be w, w+, a, a+
2. Use exec("echo '' > The file name to be created"); This is to use the system method to create the file. You can also use the touch Linux command to create
Q: Why can't I create the file?
Answer: 1. If you use fopen to create a file, do you use the parameters correctly?
2. For system permission issues, please ask your WEBMASTER whether your FTP directory has write permissions
3. FTP permission problem. You need to confirm that the directory where the file where your PHP file is to be written must have write permission. That is, the other group must have write permission after logging in to your FTP software.
If not, please modify the permission and try again.
Q: How to read a file into an array?
A: Use file
Q: How to read out all the files?
Answer: 1. Use fread($fp);
2. If your PHP version >=4.3.0, you can use file_get_contents();
Q: How to judge Does the file exist?
Answer: Use file_exists(); why not use fopen() to judge? The reason is that sometimes the data returned by fopen leads us to wrong judgments due to permission issues.
Q: Why do I get an error when I read a WEB page?
Answer: 1. It may be that your transmission parameters are wrong. When reading a WEB page, you can only use r mode to read the page
2. Make sure the WEB page you want to read Accessible
Q: How can I get the relevant attributes of a file?
Answer: PHP provides a set of methods to obtain file attributes, such as filemtime(), fileowner(), filegroup(), filectime(), fileatime()... Please refer to the detailed usage
manual.
Q: After opening a file in PHP, can I position the file "cursor" like C?
A: Yes, use fseek();
Q: I want to not allow others to access the file when accessing it, what should I do?
Answer: 1. You can use other programs to restrict users from accessing the page for file operations
2. Use flock(); for detailed parameters and usage, please refer to the manual
Q : How to delete the first line in the file, or specify a line of data?
Answer: PHP does not provide such an operation method, but we can use it in combination. The following code demonstrates that we will delete the third line of data in the file "test.dat" (test.datw
file There are more than three lines of data in it)

Copy code The code is as follows:

$filename="test .dat";//Define the operation file
$delline=3; //The number of lines to be deleted
if(!file_exsits($filename)){ 
die("The specified file was not found! The operation was interrupted !"); 
} 
$farray=file($filename);//Read file data into the array
for($tmpa=0;$Tmpaif(strcmp($Tmpa+1,$delline)==0){ 
//Judge the deleted rows
continue; 
} 
//Reorganized data 
$newfp.=$farray[$Tmpa]."rn"; 
} 
$fp=@fopen($filename,"a") or die("Failed to open file $filename in write mode" );//We open the file for writing 
@fputs($fp,$newfp) or die("File writing failed"); 
@fclose($fp); 
?> 

The above code demonstrates deleting a line of a file, but if you look carefully, it actually provides you with relevant reminders for other file operations~
Q: When I try to open a file that does not exist , how do I not let the error show up to avoid my path being leaked! !
Answer: Add the @ symbol before the method you want to open the file to block errors. @ is a special symbol provided by PHP to block error messages
Or you can add it before the step you want to operate (usually after Top of page) error_reporting(0); used to block the display of all error messages on the page
A not recommended method is to modify php.ini (except ISP)
Q: I am using a virtual host , how do I prevent other users from stealing my data?
Answer: It is recommended that ISP modify open_basedir in php.ini for restrictions.
The not recommended ISP setting is to add file operations such as fopen and file to disable_function.
Q: Why can’t I delete these files after I use PHP to delete them when I log in via FTP? ?
Answer: Mainly because the files created by PHP belong to the WEB user group, that is, the files created do not belong to your FTP user! ! !
The solution to this problem is to use chmod, unlink, etc. of the PHP program. It is recommended that users
remember the chmod file permissions when using PHP to create files. It is recommended to be 777
Q: How Using text files as data warehouse? Some guestbooks, forums, etc. all use this!
Answer: In fact, this is just a typical example of using file and combining it with explode to read and split data.
Q: How to change the file name?
Answer: rename();
Q: How to delete files?
Answer: unlink(); exec("del(rm -vf) filename"); Note: rm -vf is used under Linux
Q: How to clear the file?
Answer: Use fopen(filename,"w"); or exec("echo '' > filename");
Q: How to edit the file content?
Answer: I remember I answered a question about deleting file content before. In fact, editing content only requires variable substitution based on deleting the content.
I hope you can look up and change my continue above to replace the variable data:)