This is an example of a user defined function written by PHP DEVELOPER When you execute the above piece of code, the variable name will be added to the text that will be printed on the screen as shown below When you execute the above program, the text defined in the function will be executed An Example of a user defined function which passes a variable The structure of a user-defined function in PHP is as follows User-defined functions in PHP are also used when you do not keep repeating the same piece of code over and over again In most cases, if you want to keep your code simple and clean, it is recommended that you create functions and store them in different files such that when you need to use the code, you will not have to re-write the code again rather you will call the function name and pass parameters to it and then it will return the result User-defined functions in PHP are those functions that a developer decides to create so that they can be reused across different files in the same program or application The number of in-built functions is not clearly defined but it is estimated that they are more than 1000 in-built functions that are supported by PHP. Learn how you can upload multiple files using PHP and jQuery move_uploaded_file() function that is used to upload a file to a server.Learn how str_replace() function is used to remove white spaces from a string str_replace() which is used to remove white spaces from a string.View how you can calculate the length of a string in PHP strlen() is used to determine the length of a string.Some examples of inbuilt functions in PHP language are as follows In-built PHP functions are functions that are provided by PHP language that when called, execute depending on the purpose of the defined function. Please note that functions in PHP must have () after the name of the function, the syntax for a PHP function is function_name() In-built functions in PHP There are two types of functions that are supported in the PHP programming language, that is in-built functions and user-defined functions. Wampserver 2.1, Apache 2.2.17, PHP 5.2.In PHP programming language which is one of the back end or server-side programming languages, functions are used at every step to ensure that the code is compiled and executed successfully.Ī function in PHP is an already defined or compiled piece of code that does or performs a specific action when it is called in a block of code.I have tested the above values in following environments: Var $var (a variable declared, but without a value) The blank spaces means the function returns bool(false). The table below is an easy reference for what these functions will return for different values. is_null() is opposite of isset(), except for one difference that isset() can be applied to unknown variables, but is_null() only to declared variables. In other words, it returns true only when the variable is null. Is_null - Finds whether a variable is NULL In other words, it will return true if the variable is an empty string, false, array(), NULL, “0?, 0, and an unset variable. empty()Įmpty - Determine whether a variable is empty ![]() In other words, it returns true only when the variable is not null. Isset - Determine if a variable is set and is not NULL In this post I will explain the differences between these functions. Isset() and empty() are often viewed as functions that are opposite, however this is not always true. ![]() ![]() If these functions are not used in correct way they can cause unexpected results. ![]() All these function return a boolean value. Three useful functions for this are isset(), empty() and is_null(). PHP has different functions which can be used to test the value of a variable.
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