The real power of PHP comes from its functions. Show
PHP has more than 1000 built-in functions, and in addition you can create your own custom functions. PHP Built-in FunctionsPHP has over 1000 built-in functions that can be called directly, from within a script, to perform a specific task. Please check out our PHP reference for a complete overview of the PHP built-in functions. PHP User Defined FunctionsBesides the built-in PHP functions, it is possible to create your own functions.
Create a User Defined Function in PHPA user-defined function declaration starts with the word Syntax function functionName() { Note: A function name must start with a letter or an underscore. Function names are NOT case-sensitive. Tip: Give the function a name that reflects what the function does! In the example below, we create a function named "writeMsg()". The opening curly brace ( { ) indicates the beginning of the function code, and the closing curly brace ( } ) indicates the end of the function. The function outputs "Hello world!". To call the function, just write its name followed by brackets (): Example<?php writeMsg(); // call the function Try it Yourself » PHP Function ArgumentsInformation can be passed to functions through arguments. An argument is just like a variable. Arguments are specified after the function name, inside the parentheses. You can add as many arguments as you want, just separate them with a comma. The following example has a function with one argument ($fname). When the familyName() function is called, we also pass along a name (e.g. Jani), and the name is used inside the function, which outputs several different first names, but an equal last name: Example<?php familyName("Jani"); Try it Yourself » The following example has a function with two arguments ($fname and $year): Example<?php familyName("Hege", "1975"); Try it Yourself » PHP is a Loosely Typed LanguageIn the example above, notice that we did not have to tell PHP which data type the variable is. PHP automatically associates a data type to the variable, depending on its value. Since the data types are not set in a strict sense, you can do things like adding a string to an integer without causing an error. In PHP 7, type declarations were added. This gives us an option to specify the expected data type when declaring a function, and by adding the In the following example we try to send both a number
and a string to the function without using Example<?php Try it Yourself » To specify In the following example we try to send both a number and a string to the function, but here we have added the Example<?php declare(strict_types=1); // strict requirement function addNumbers(int $a, int $b) { Try it Yourself » The PHP Default Argument ValueThe following example shows how to use a default parameter. If we call the function setHeight() without arguments it takes the default value as argument: Example<?php declare(strict_types=1); // strict requirement setHeight(350); Try it Yourself » PHP Functions - Returning valuesTo let a function return a value, use the Example<?php
declare(strict_types=1); // strict requirement echo "5 + 10 = " . sum(5, 10) . "<br>"; Try it Yourself » PHP Return Type DeclarationsPHP 7 also supports Type Declarations
for the To declare a type for the function return, add a colon ( In the following example we specify the return type for the function: Example<?php declare(strict_types=1); // strict
requirement Try it Yourself » You can specify a different return type, than the argument types, but make sure the return is the correct type: Example<?php declare(strict_types=1); // strict requirement Try it Yourself » Passing Arguments by ReferenceIn PHP, arguments are usually passed by value, which means that a copy of the value is used in the function and the variable that was passed into the function cannot be changed. When a
function argument is passed by reference, changes to the argument also change the variable that was passed in. To turn a function argument into a reference, the ExampleUse a pass-by-reference argument to update a variable: <?php $num = 2; Try it Yourself » PHP ExercisesHow can I call a function in PHP?There are two methods for doing this. One is directly calling function by variable name using bracket and parameters and the other is by using call_user_func() Function but in both method variable name is to be used. call_user_func( $var );
How do you define a function and call it in PHP?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 will not execute automatically when a page loads. A function will be executed by a call to the function.
How do you call a PHP function in HTML?Calling a PHP function using the HTML button: Create an HTML form document which contains the HTML button. When the button is clicked the method POST is called. The POST method describes how to send data to the server. After clicking the button, the array_key_exists() function called.
How are function created in PHP?Creating and Calling Function
In PHP, the function name is any name that ends in an open and closed parenthesis. The keyword function is often used to start a function name. To invoke a function, simply type its name followed by the parenthesis. A number cannot be the first character in a feature name.
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