Introduction to custom functions of PHP functions_PHP tutorial

In PHP, more than 700 built-in functions are provided. PHP functions are divided into user-defined functions and system built-in functions. Built-in functions can be used directly, and user-defined functions need to be defined using the keyword function.

Custom function
A function can be seen as a collection of independent program statements that implement a certain function. After we write a certain function into a function, we can use it conveniently where needed. Reasonable use of functions can make our PHP programs more concise, easy to read, and more scientific.
Grammar

Example

The code is as follows

代码如下	复制代码
function function_name(arg1,arg2,……) {     函数功能代码 }

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function function_name(arg1,arg2,……) {

Function code
}





Create PHP function
A function is a block of code that can be executed whenever needed.

Create PHP function:
All functions start with the keyword "function()"

Naming functions - The name of a function should hint at its functionality. Function names start with a letter or underscore.

代码如下	复制代码
function writeMyName() { echo "David Yang"; } echo "Hello world! "; echo "My name is "; writeMyName(); echo ". That's right, "; writeMyName(); echo " is my name."; ?> 以上代码的输出： Hello world! My name is David Yang. That's right, David Yang is my name.

Add "{" - the part after the opening curly brace is the function's code.

Insert function code
Add a "}" - the function ends by closing the curly brace.

Function parameters

代码如下	复制代码
function city_name($city) { echo "城市名称为：".$city; } city_name("shanghai"); //执行该函数，执行结果是输出“城市名称为：shanghai”字符串 ?> 可以给函数的参数指定默认值，以便在没有指定参数值时，采用参数默认值。 function city_name($city = "beijing") { echo "城市名称为：".$city; } $name = "shanghai"; city_name(); //执行结果是输出“城市名称为：beijing” city_name($name); //执行结果是输出“城市名称为：shanghai” ?>

The function of parameters is to pass information to the function.

Now, we are going to use this function in our PHP script:

The code is as follows

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function writeMyName() { echo "David Yang"; } echo "Hello world!
"; echo "My name is "; writeMyName(); echo ".
That's right, ";

writeMyName();

echo " is my name."; ?> Output of the above code: Hello world! My name is David Yang. That's right, David Yang is my name. Example:

The code is as follows

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function city_name($city)<🎜> {<🎜> echo "The city name is: ".$city;<🎜> }<🎜> city_name("shanghai"); //Execute this function, the execution result is to output the string "The name of the city is: shanghai"<🎜> ?> You can specify default values ​​for function parameters so that when no parameter value is specified, the parameter default value is used. function city_name($city = "beijing")<🎜> {<🎜> echo "The city name is: ".$city;<🎜> }<🎜> $name = "shanghai";<🎜> city_name(); //The execution result is the output "The city name is: beijing"<🎜> city_name($name); //The execution result is to output "The city name is: shanghai"<🎜> ?> http://www.bkjia.com/PHPjc/629078.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/629078.htmlTechArticleIn PHP, more than 700 built-in functions are provided. PHP functions are divided into user-defined functions and system built-in functions. Built-in functions can be used directly, user-defined functions need to use...