What is the difference between php and js?

There are differences between PHP and JS in the way of embedding pages, output syntax, data types, as well as defining variables, string splicing, type conversion, etc. Please refer to the following for more information. I hope it will be helpful to everyone.

1. Embedding page method

JS embedding method:

<script></script>

PHP embedding method:

<?php     
?>(常用)

2. Output syntax

Javascript output

alert("警告的内容")
prompt("提示的内容")
document.write()(页面输出内容)

PHP output

echo（常用）//可同时输出多个字符串　　
print　　//只能输出一个字符串　　　　　 
print_r();//可以打印数组
var_dump();//可输出变量的内容、类型和长度

3.Data type

JS Data Type

● Integer type (integer) int

● Single precision decimal float

● Double precision decimal double

● Decimal decimal

● Boolean bool (can only store two states)

● Date and time type datetime

● Character char (not commonly used) strong

● String string (not commonly used) strong

PHP data type

● bool Boolean type (storage two states)

●int Integer type

●float(double) Floating point type

●char Character

●string String

4. Define variables

JS Define variables:

var a = 10;

Note: If you define an integer or decimal variable, the value after the equal sign is written directly; if you define a string variable, the value after the equal sign needs to be enclosed in double quotes or single quotes)

PHP defines variables:

$a = 5；　　$a = "hello"；　　$a = <<<A　

Note: If you define an integer or decimal variable, the value after the equal sign is written directly; if you define a string variable, the value after the equal sign needs to be enclosed in double quotes or single quotes. )

5. String splicing

String splicing in JS: use ""

eg：

"hello"+"world"

PHP String splicing: use "."

eg:

"hello"."world"

6. Case issues

js is strictly case-sensitive

## Custom function names in #php are not case sensitive. When naming a function, you cannot use declared functions or PHP's built-in function names.

7. The difference between control statements

else if and elseif are both supported in php, js only supports the former

8. Data Differences in types

There is an undefined type in js, but there is no such type in php.

So when a variable is not assigned any value, this type in js is undefined (use undeclared The variable will report an error), but in php it is of Null type;

And there is only number type in js, but there is no such type in php, replaced by int float type;

9. Type conversion

Type conversion in JS

转化为整数：parseInt();
转化为小数：parseFloat();
判断是否为合法数字类型：isNaN();

Type conversion in PHP

$a = (Int)$a;　　//强制转化变量a为整数
$b = settype($b,"string");　　//强制转化变量a为字符串

10. Differences in actual parameters

In js, there is no limit to the number of formal parameters and actual parameters. The number of formal parameters can be greater than the actual parameters, or it can be less than the actual parameters

And in php, the number of actual parameters If the parameters are greater than the formal parameters, no error will be reported, but when the number of actual parameters is less than the number of formal parameters (and an error will be reported when the unspecified formal parameters are undefined)

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