Introduction to PHP function examples

In this article, we mainly share with you an introduction to PHP function examples. We mainly briefly introduce the concept of PHP functions and how to use them. We hope it can help everyone.

Naming:Just follow the variable naming rules. Functions cannot be overloaded.

Function:The function implements structured programming and improves Improves the maintainability of the code

Global variables:Can be used throughout the script.

Local variables:Defined in the function body, only used within the function body, automatically released after the function is executed

is divided into static storage type and dynamic Storage type; static $a is a static variable, which will not be released after the function is executed.

Local variables within the function Programming global variables: 1.global; 2.$GLOBAL ['']Use global array

Type of function

1. Function with custom parameters:

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2. Functions that reference parameters:

Function test( &$a ) { } //$a is a reference variable , relative to external variables, if $a is modified internally in the function, the external variables are also modified.

3. Function with default parameters:

fuction test($a=0) { } //$a=0 Indicates that when calling a function, no actual parameters are passed to the function, then the default $a=0;

4. Functions with variable number of parameters:

Function test(){$a,$b,...}{ } //Principle: Through the func_get_args() function, all parameters are accepted and a data is returned for use, so there can be multiple Parameters

## func_get_args() gets the parameter array,func_num_args() gets the number of parameters,func_get_arg() returns the specified parameters (generally used in conjunction with func_num_args )

5. Callback function: function one(){} $fun="one"; When $fun( is executed, it is equivalent to calling the one() function;

6. Recursive function: In the function body, when calling the function itself, remember that there must be an exit, that is, exit conditions, otherwise an infinite loop will form.

function test($a){ if（$a >=0 ）{ //退出递归的条件，一定要有 test($a-1); }else{ return ; } }

7. Anonymous function: It is a function without a name, generally used for callback functions. fucntion($a){ }

Commonly used functions:

echo()【语言结构】 print()//【语言结构】【有返回值】，若传输失败导致没有输出，它返回false var_dump() var_export()【有返回值，翻译一个合法的PHP 代码】 printf()//类似与C 语言的形式 printf("my name is %s, age %d", $name, $age);,打印出来 sprintf()//跟printf 相似，但不打印，而是返回格式化后的文字，其他的与printf 一样

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