PHP About files and directories (1) Writing files File permissions 3. Locking files

1. File permissions

In short, everything is to ensure the security of the directory. Ensuring the security of the directory is more important than ensuring the security of the files.

2. Write file

file_put_contents($file,$data); //If not, it will be created, if there is, the original file will be overwritten;

file_put_contents($file,$data,FILE_APPEND); //If not, it will be created, if there is, it will be appended;

file_put_contents($file,$data.PHP_EOL,FILE_APPEND);//With line breaks

[Example]:

// Identify the file to use:
$file ='../quotes.txt'; //This file is best placed in the parent directory for safety.

// Check for a form submission:
if ($_SERVER['REQUEST_METHOD'] == 'POST') { // Handle theform.

if ( !empty($_POST['quote'])&& ($_POST['quote'] != 'Enter yourquotation here.') ) { // Need some thing to write.

if(is_writable($file)) { // Confirm that the file iswritable.

file_put_contents($file,$_POST['quote'] . PHP_EOL, FILE_APPEND); // Write thedata.

//Print amessage:
print'

Your quotation has beenstored.

} else { // Could notopen the file.
print'

Yourquotation could not be stored due to a systemerror.

} else { // Failed to enter aquotation.
print 'Please enter aquotation!=color:>

} // End of submitted IF.

// Leave PHP and display the form:
?>

3. Lock files

file_put_contents($file,$data,FILE_APPEND|LOCK_EX); //The order in which the two variables are used does not matter

LOCK_SH Shared lock for reading

LOCK_EX Exclusive lock for writing

LOCK_UN Release a lock

LOCK_NB Non-blocking lock

4. Read files

The first method: $data=file_get_contents($file); //Read according to a string

The second method: $data=file($file); //Read the data of each line, which is more commonly used

[Example]: //Additional: Be cautious and you can use the is_readable() function before the file function to test whether the file is readable

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RandomQuetation

// Count the number of items in the array:
$n = count($data);

//Pick a random item: Generate a random number
$rand = rand(0, ($n -1));

// Print the quotation:
print '

' .trim($data[$rand]) .'

?>