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1. www.php.net › manual › enPHP: defined - Manual

   www.php.net › manual › en

   Checks whether a constant with the given constant_name is defined. This function works also with class constants and enum cases. Note: If you want to see if a variable exists, use isset () as defined () only applies to constants. If you want to see if a function exists, use function_exists ().

   • Uniqid

     Caution This function does not generate cryptographically...

   • Exit

     Notes ¶ Warning Prior to PHP 8.4.0, exit () was a language...

   • Sleep

     Delay execution Delays the program execution for the given...

   • Unpack

     Unpack data from binary string

   • Usleep

     Parameters ¶ microseconds Halt time in microseconds. A...

   • Pack

     Pack given arguments into a binary string according to...

   • Hrtime

     hrtime (PHP 7 >= 7.3.0, PHP 8) hrtime — Get the system's...

   • Constant

     Return the value of the constant indicated by name. constant...

2. www.w3schools.com › php › php_functionsPHP Functions - W3Schools

   www.w3schools.com › php › php_functions

   PHP User Defined Functions Besides the built-in PHP functions, it is possible to create your own functions. A function is a block of statements that can be used repeatedly in a program. A function is not executed automatically when a page loads. A function is executed only when it is called.

3. phplang.org › spec › 13-functionsFunctions - PHP Language Specification

   phplang.org › spec › 13-functions

   Functions General When a function is called, information may be passed to it by the caller via an argument list, which contains one or more argument expressions, or more simply, arguments. These correspond by position to the parameters in a parameter list in the called function’s definition. An unconditionally defined function is a function whose definition is at the top level of a script. A ...

4. www.bomberbot.com › php › php-defined-function-an-inPHP defined () Function: An In-Depth Exploration - Bomberbot

   www.bomberbot.com › php › php-defined-function-an-in

   Aug 21, 2025 · PHP's defined () function is a fundamental tool that every developer should master. This powerful yet simple function allows you to check for the existence of constants in your code, providing a crucial safeguard against errors and enabling more flexible and robust applications.

5. www.tutorialrepublic.com › php-tutorial › phpHow to Define and Call a Function in PHP - Tutorial Republic

   www.tutorialrepublic.com › php-tutorial › php

   In this tutorial you will learn how to define and call a custom function in PHP to save the repetition of code and make your code much easier to maintain.

6. www.w3schools.com › PHP › func_misc_definePHP define () Function - W3Schools

   www.w3schools.com › PHP › func_misc_define

   Well organized and easy to understand Web building tutorials with lots of examples of how to use HTML, CSS, JavaScript, SQL, Python, PHP, Bootstrap, Java, XML and more.

7. People also ask

   What is a PHP function?

   • A PHP function is a piece of reusable code. It may take input as an argument (or parameter) and return a value after some processing. You may have already seen some functions in our previous tutorials, as they are widely used. The following piece of code shows the syntax of a function.

   PHP Functions: Classifications, Parameters and More

   www.softwaretestinghelp.com/php/php-functions/

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   How many functions are there in PHP?

   • There are over 1000 built-in functions available in PHP, and you can also build your functions. PREV Tutorial | NEXT Tutorial Was this helpful? This Tutorial Explains What Are Functions in C# Programming With Simple Examples.

   PHP Functions: Classifications, Parameters and More

   www.softwaretestinghelp.com/php/php-functions/

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   Can I create my own PHP functions?

   • Besides the built-in PHP functions, it is possible to create your own functions. A function is a block of statements that can be used repeatedly in a program. A function is not executed automatically when a page loads. A function is executed only when it is called.

   PHP Functions - W3Schools

   www.w3schools.com/php/php_functions.asp

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   What is a function definition?

   • A function-definition defines a function called name. Function names are not case-sensitive. A function can be defined with zero or more parameters, each of which is specified in its own parameter-declaration in a parameter-declaration-list. Each parameter has a name, variable-name, and optionally, a default-argument-specifier.

   Functions - PHP Language Specification

   phplang.org/spec/13-functions

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8. www.softwaretestinghelp.com › php › php-functionsPHP Functions: Classifications, Parameters and More

   www.softwaretestinghelp.com › php › php-functions

   Jul 4, 2025 · PHP Functions are blocks of reusable code that are designed to perform a specific task. Understand its Classifications, Arguments & default values with simple examples: In this tutorial, you will learn what a PHP function is, built-in functions (such as PHP empty (), count (), etc.), user-defined functions, parameters, arguments & default values, returning values, recursive & anonymous PHP ...