Summary of new features of PHP7.4

PHP7.4 New Features

PHP7.4 has been released. Brought some new features. This allows us to write less code.

1. Add qualified type to attributes

age = 10;
$user->name = "张三";
//error
$user->age = "zhang";//需要传递int

2. Arrow function

This feature basically refers to the syntax of ES6 in Js. This allows us to write less code. If your code has the function fn. May conflict

$n * $factor,[1,2,3]);//[10,20,30]
//之前的写法
$nums = array_map(function($num)use($factor){
  return $num * $factor;
},[1,2,3])

3. Limited return type covariance and parameter type contravariance

Full covariance/contravariance support is only provided when using autoloading. Within a single file, only non-cyclic type references can be used, since all classes must be available before being referenced.

4. Array unpacking

Use the spread operator... to unpack the array. This feature should be absorbed from js. See example

5. Null coalescing operator assignment
6. Numeric literal delimiter
 
Number literals can contain underscores between numbers. 
7. Allow exceptions to be thrown from __toString() 
 Now allows exceptions to be thrown from __toString(). In the past this would result in a fatal error. Existing recoverable in string conversion Fatal errors have been converted to Error exceptions. 
8. Filter
Added FILTER_VALIDATE_FLOAT
9. strip_tags supports arrays
");
废弃的特性
1. 没有显式括号的嵌套三元运算符
During the interview, Finally, I don’t have to worry about asking you what the result is. In fact, in production, everyone will not write like this. 
2. Curly braces to access array index
"111"];
$index = "a";
$arr{$index}//废弃
$arr[$index];
To be honest, this is the first time I have seen it and it has been abandoned. , indicating that no one will use it this way. 
3. real and is_real real numbers
4. The parent keyword is used in a class without a parent class
If parent is used in a class without a parent class, compilation will occur. mistake. 
5. money_format function
money_format is deprecated and replaced by numberFormater
6. Removed extensions
1.Firebird/Interbase
2.Recode
3.WDDX

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