- PHP Tutorial
- PHP - Home
- PHP - Introduction
- PHP - Installation
- PHP - History
- PHP - Syntax
- PHP - Hello World
- PHP - Comments
- PHP - Variables
- PHP - Echo/Print
- PHP - var_dump
- PHP - $ and $$ Variables
- PHP - Constants
- PHP - Magic Constants
- PHP - Data Types
- PHP - Type Casting
- PHP - Type Juggling
- PHP - Strings
- PHP - Boolean
- PHP - Integers
- PHP - Files & I/O
- PHP - Maths Functions
- PHP - Heredoc & Nowdoc
- PHP - Compound Types
- PHP - File Include
- PHP - Date & Time
- PHP - Scalar Type Declarations
- PHP - Return Type Declarations
- PHP Operators
- PHP - Operators
- PHP - Arithmatic Operators
- PHP - Comparison Operators
- PHP - Logical Operators
- PHP - Assignment Operators
- PHP - String Operators
- PHP - Array Operators
- PHP - Conditional Operators
- PHP - Spread Operator
- PHP - Null Coalescing Operator
- PHP - Spaceship Operator
- PHP Control Statements
- PHP - Decision Making
- PHP - If…Else Statement
- PHP - Switch Statement
- PHP - For Loop
- PHP - Foreach Loop
- PHP - While Loop
- PHP - Do…While Loop
- PHP - Break Statement
- PHP - Continue Statement
- PHP Arrays
- PHP - Arrays
- PHP - Indexed Array
- PHP - Associative Array
- PHP - Multidimensional Array
- PHP - Array Functions
- PHP - Constant Arrays
- PHP Functions
- PHP - Functions
- PHP - Function Parameters
- PHP - Call by value
- PHP - Call by Reference
- PHP - Default Arguments
- PHP - Named Arguments
- PHP - Variable Arguments
- PHP - Returning Values
- PHP - Passing Functions
- PHP - Recursive Functions
- PHP - Type Hints
- PHP - Variable Scope
- PHP - Strict Typing
- PHP - Anonymous Functions
- PHP - Arrow Functions
- PHP - Variable Functions
- PHP - Local Variables
- PHP - Global Variables
- PHP Superglobals
- PHP - Superglobals
- PHP - $GLOBALS
- PHP - $_SERVER
- PHP - $_REQUEST
- PHP - $_POST
- PHP - $_GET
- PHP - $_FILES
- PHP - $_ENV
- PHP - $_COOKIE
- PHP - $_SESSION
- PHP File Handling
- PHP - File Handling
- PHP - Open File
- PHP - Read File
- PHP - Write File
- PHP - File Existence
- PHP - Download File
- PHP - Copy File
- PHP - Append File
- PHP - Delete File
- PHP - Handle CSV File
- PHP - File Permissions
- PHP - Create Directory
- PHP - Listing Files
- Object Oriented PHP
- PHP - Object Oriented Programming
- PHP - Classes and Objects
- PHP - Constructor and Destructor
- PHP - Access Modifiers
- PHP - Inheritance
- PHP - Class Constants
- PHP - Abstract Classes
- PHP - Interfaces
- PHP - Traits
- PHP - Static Methods
- PHP - Static Properties
- PHP - Namespaces
- PHP - Object Iteration
- PHP - Encapsulation
- PHP - Final Keyword
- PHP - Overloading
- PHP - Cloning Objects
- PHP - Anonymous Classes
- PHP Web Development
- PHP - Web Concepts
- PHP - Form Handling
- PHP - Form Validation
- PHP - Form Email/URL
- PHP - Complete Form
- PHP - File Inclusion
- PHP - GET & POST
- PHP - File Uploading
- PHP - Cookies
- PHP - Sessions
- PHP - Session Options
- PHP - Sending Emails
- PHP - Sanitize Input
- PHP - Post-Redirect-Get (PRG)
- PHP - Flash Messages
- PHP AJAX
- PHP - AJAX Introduction
- PHP - AJAX Search
- PHP - AJAX XML Parser
- PHP - AJAX Auto Complete Search
- PHP - AJAX RSS Feed Example
- PHP XML
- PHP - XML Introduction
- PHP - Simple XML Parser
- PHP - SAX Parser Example
- PHP - DOM Parser Example
- PHP Login Example
- PHP - Login Example
- PHP - Facebook Login
- PHP - Paypal Integration
- PHP - MySQL Login
- PHP Advanced
- PHP - MySQL
- PHP.INI File Configuration
- PHP - Array Destructuring
- PHP - Coding Standard
- PHP - Regular Expression
- PHP - Error Handling
- PHP - Try…Catch
- PHP - Bugs Debugging
- PHP - For C Developers
- PHP - For PERL Developers
- PHP - Frameworks
- PHP - Core PHP vs Frame Works
- PHP - Design Patterns
- PHP - Filters
- PHP - JSON
- PHP - Exceptions
- PHP - Special Types
- PHP - Hashing
- PHP - Encryption
- PHP - is_null() Function
- PHP - System Calls
- PHP - HTTP Authentication
- PHP - Swapping Variables
- PHP - Closure::call()
- PHP - Filtered unserialize()
- PHP - IntlChar
- PHP - CSPRNG
- PHP - Expectations
- PHP - Use Statement
- PHP - Integer Division
- PHP - Deprecated Features
- PHP - Removed Extensions & SAPIs
- PHP - PEAR
- PHP - CSRF
- PHP - FastCGI Process
- PHP - PDO Extension
- PHP - Built-In Functions
- PHP Useful Resources
- PHP - Questions & Answers
- PHP - Useful Resources
- PHP - Discussion
PHP - Function flock()
The flock() function can lock or release a file, and it can return true on success or false on failure.
Syntax
bool flock ( resource $handle , int $operation [, int &$wouldblock ] )
The flock() function allows us to perform a simple reader/writer model that can be used on virtually every platform.
The possible locks are LOCK_SH:Shared lock (reader). Allow other processes to access the file, LOCK_EX: Exclusive lock.Prevent other processes from accessing file, LOCK_UN: Release a shared or exclusive lock, and LOCK_NB: Avoids blocking other processes while locking.
These locks are used only in the current PHP process, and if the permission allows, other processes can modify or delete the PHP-locked file. This function is mandatory under Windows. We can use the fclose () function to release the lock operation, which can be automatically called when the script execution is completed.
Example
<?php $file = fopen("/PhpProject/sample.txt", "w+"); // exclusive lock if(flock($file, LOCK_EX)) { fwrite($file, "flock function"); // release lock flock($file, LOCK_UN); echo $file; } else { echo "Error locking file!"; } fclose($file); ?>