Methods for passing parameters by PHP functions: 1. Pass by value, copy the value of the actual parameter and then pass it to the formal parameter of the function; 2. Pass by reference, copy the memory address of the actual parameter and pass it For formal parameters of the function; 3. Default parameters, specify a default value for one or more formal parameters of the function; 4. Variable length parameters, which will be passed to the function as an array.
The operating environment of this tutorial: windows7 system, PHP7.1 version, DELL G3 computer
When calling a function, you need to pass parameters to the function , the parameters passed into the function are called actual parameters, and the parameters defined by the function are called formal parameters. There are four ways to pass parameters to a function, namely passing by value, passing by reference, default parameters and variable length parameters.
1. Value passing
Value passing is the default value passing method for functions in PHP, also known as "copy passing by value". As the name suggests, the value passing method will copy the value of the actual parameter and then pass it to the formal parameter of the function, so operating the value of the parameter in the function will not affect the actual parameters outside the function. Therefore, if you do not want the function to modify the value of the actual parameter, you can pass it by value.
[Example] The following defines a simple function. The function has two parameters, and the values of the parameters are exchanged in the function.
<?php function swap($a, $b){ echo '函数内,交换前 $a = '.$a.', $b = '.$b.'<br>'; $temp = $a; $a = $b; $b = $temp; echo '函数内,交换后 $a = '.$a.', $b = '.$b.'<br>'; } $x = 5; $y = 7; echo '函数外,交换前 $x = '.$x.', $y = '.$y.'<br>'; swap($x, $y); echo '函数外,交换后 $x = '.$x.', $y = '.$y; ?>
The running results are as follows:
函数外,交换前 $x = 5, $y = 7 函数内,交换前 $a = 5, $b = 7 函数内,交换后 $a = 7, $b = 5 函数外,交换后 $x = 5, $y = 7
It can be seen from the running results that the values are indeed exchanged within the function, but outside the function, the values do not change. So we can say that passing a function by value is just passing a copy of the variable. So if you want the function to be able to operate on external parameters of the function, you need to use reference passing.
2. Passing by reference
Passing by reference is to copy the memory address of the actual parameter and then pass it to the formal parameter, actual parameter and formal parameter of the function. They all point to the same memory address, so the function's operation on the formal parameters will affect the actual parameters outside the function.
Passing by reference is to pass the memory address of the actual parameter to the formal parameter of the function. Therefore, the actual parameters and formal parameters point to the same memory address. At this time, all operations inside the function will affect the values of the actual parameters outside the function. The method of passing by reference is to add an & symbol on the basis of value passing, as shown below:
function name (&参数1, &参数2, ..., &参数3) { ... }
[Example] Slightly adjust the code of the above example and use the method of passing by reference to pass to the swap function. Parameters, the code is as follows:
<?php function swap(&$a, &$b){ echo '函数内,交换前 $a = '.$a.', $b = '.$b.'<br>'; $temp = $a; $a = $b; $b = $temp; echo '函数内,交换后 $a = '.$a.', $b = '.$b.'<br>'; } $x = 5; $y = 7; echo '函数外,交换前 $x = '.$x.', $y = '.$y.'<br>'; swap($x, $y); echo '函数外,交换后 $x = '.$x.', $y = '.$y; ?>
The running result is as follows:
函数外,交换前 $x = 5, $y = 7 函数内,交换前 $a = 5, $b = 7 函数内,交换后 $a = 7, $b = 5 函数外,交换后 $x = 7, $y = 5
3. Default parameters
The default parameter is a certain or Multiple formal parameters specify a default value. If the corresponding value is not passed in when calling the function, the function will use this default value. This can avoid errors when calling without parameters, and can also make some programs more reasonable. If the corresponding parameters are passed in, this default value will be replaced.
The default parameters of the function are as follows:
function name ($str = 'PHP中文网', $url) { echo $str; }
Among them, the "PHP Chinese Network" after the formal parameter $str is its default value, and the = connection needs to be used between the formal parameters and the default values. .
[Example] Let’s define a function with default parameters as follows:
<?php function add($a, $b=56){ echo $a.' + '.$b.' = '.($a+$b).'<br>'; } add(11); add(37, 29); ?>
The running result is as follows:
11 + 56 = 67 37 + 29 = 66
The default parameters can also be multiple, and The default parameter must be placed to the right of the non-default parameter, and the value of the specified default parameter must be a specific value, such as a number or a string, rather than a variable.
[Example] Let’s define a function with multiple default parameters as follows:
<?php function add($a, $b=33, $c=57){ echo $a.' + '.$b.' + '.$c.' = '.($a+$b+$c).'<br>'; } add(11); add(31, 22); add(64, 9, 7); ?>
The running result is as follows:
11 + 33 + 57 = 101 31 + 22 + 57 = 110 64 + 9 + 7 = 80
4. Variable Length parameter
In PHP 5.6 and later versions, the formal parameters of the function can use... to indicate that the function can accept a variable number of parameters, and the variable parameters will be passed as an array Give function. An example is as follows:
<?php function test(...$arr){ print_r($arr); } echo '<pre class="brush:php;toolbar:false">'; test(1, 2, 3, 4); test(5, 6, 7, 8, 9, 10); ?>
The running results are as follows:
Array ( [0] => 1 [1] => 2 [2] => 3 [3] => 4 ) Array ( [0] => 5 [1] => 6 [2] => 7 [3] => 8 [4] => 9 [5] => 10 )
Recommended learning: "PHP Video Tutorial"
The above is the detailed content of What are the ways to pass parameters to functions in php?. For more information, please follow other related articles on the PHP Chinese website!

php把负数转为正整数的方法:1、使用abs()函数将负数转为正数,使用intval()函数对正数取整,转为正整数,语法“intval(abs($number))”;2、利用“~”位运算符将负数取反加一,语法“~$number + 1”。

实现方法:1、使用“sleep(延迟秒数)”语句,可延迟执行函数若干秒;2、使用“time_nanosleep(延迟秒数,延迟纳秒数)”语句,可延迟执行函数若干秒和纳秒;3、使用“time_sleep_until(time()+7)”语句。

php除以100保留两位小数的方法:1、利用“/”运算符进行除法运算,语法“数值 / 100”;2、使用“number_format(除法结果, 2)”或“sprintf("%.2f",除法结果)”语句进行四舍五入的处理值,并保留两位小数。

判断方法:1、使用“strtotime("年-月-日")”语句将给定的年月日转换为时间戳格式;2、用“date("z",时间戳)+1”语句计算指定时间戳是一年的第几天。date()返回的天数是从0开始计算的,因此真实天数需要在此基础上加1。

方法:1、用“str_replace(" ","其他字符",$str)”语句,可将nbsp符替换为其他字符;2、用“preg_replace("/(\s|\ \;||\xc2\xa0)/","其他字符",$str)”语句。

php判断有没有小数点的方法:1、使用“strpos(数字字符串,'.')”语法,如果返回小数点在字符串中第一次出现的位置,则有小数点;2、使用“strrpos(数字字符串,'.')”语句,如果返回小数点在字符串中最后一次出现的位置,则有。

在PHP中,可以利用implode()函数的第一个参数来设置没有分隔符,该函数的第一个参数用于规定数组元素之间放置的内容,默认是空字符串,也可将第一个参数设置为空,语法为“implode(数组)”或者“implode("",数组)”。

在php中,可以使用substr()函数来读取字符串后几个字符,只需要将该函数的第二个参数设置为负值,第三个参数省略即可;语法为“substr(字符串,-n)”,表示读取从字符串结尾处向前数第n个字符开始,直到字符串结尾的全部字符。


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

AI Hentai Generator
Generate AI Hentai for free.

Hot Article

Hot Tools

EditPlus Chinese cracked version
Small size, syntax highlighting, does not support code prompt function

Dreamweaver Mac version
Visual web development tools

ZendStudio 13.5.1 Mac
Powerful PHP integrated development environment

SublimeText3 Mac version
God-level code editing software (SublimeText3)

mPDF
mPDF is a PHP library that can generate PDF files from UTF-8 encoded HTML. The original author, Ian Back, wrote mPDF to output PDF files "on the fly" from his website and handle different languages. It is slower than original scripts like HTML2FPDF and produces larger files when using Unicode fonts, but supports CSS styles etc. and has a lot of enhancements. Supports almost all languages, including RTL (Arabic and Hebrew) and CJK (Chinese, Japanese and Korean). Supports nested block-level elements (such as P, DIV),
