PHP7.4 new features and deprecated functions (summary)

Summary of new and deprecated features in PHP7.4

New features in PHP7.4

PHP7.4 was released on the 28th of last month. Brought some new features. This allows us to write less code.

1. Add qualified type to attributes

<?php
class User {
  public int $age;
  public string $name
}  
$user = new User();
$user->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

<?php
$factor = 10;
$nums = array_map(fn($n)=>$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.

<?php
class A {}
class B extends A {}
class Producer {
    public function method(): A {}
}
class ChildProducer extends Producer {
    public function method(): B {}
}
?>

4. Array unpacking

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

<?php
$parts = [&#39;apple&#39;, &#39;pear&#39;];
$fruits = [&#39;banana&#39;, &#39;orange&#39;, ...$parts, &#39;watermelon&#39;];//[&#39;banana&#39;, &#39;orange&#39;, &#39;apple&#39;, &#39;pear&#39;, &#39;watermelon&#39;];
//老的写法
$fruits = array_merge([&#39;banana&#39;, &#39;orange&#39;],$parts,[&#39;watermelon&#39;]);

5. Null coalescing operator assignment

<?php
$array[&#39;key&#39;] ??= computeDefault();
// 老的写法
if (!isset($array[&#39;key&#39;])) {
    $array[&#39;key&#39;] = computeDefault();
}
?>

6. Numeric literal separator

Numeric literals can contain underscores between numbers.

<?php
6.674_083e-11; // float
299_792_458;   // decimal
0xCAFE_F00D;   // hexadecimal
0b0101_1111;   // binary
?>

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

New FILTER_VALIDATE_FLOAT

<?php
  filter_var(1.00,FILTER_VALIDATE_FLOAT);
filter.filters.validate

9. strip_tags supports arrays

<?php
  strip_tags($str,[&#39;p&#39;,&#39;a&#39;,&#39;div&#39;]);
//老的写法
strip_tags($str,"<p><a><div>");

Deprecated features

1. Nested ternary operator without explicit brackets

<?php
1 ? 2 : 3 ? 4 : 5;   // deprecated
(1 ? 2 : 3) ? 4 : 5; // ok
1 ? 2 : (3 ? 4 : 5); // ok
?>

During the interview, I finally don’t have to worry about asking you what the result is. In fact, in production, everyone will not write like this.

2. Accessing array index using curly braces

<?php
$arr = ["a"=>"111"];
$index = "a";
$arr{$index}//废弃
$arr[$index];

To be honest, this is the first time I have seen it. It is abandoned, which means that no one will use it this way.

3. real and is_real real numbers

<?php
  $num = "";
  $a = (real) $num;//废弃
$a = (float) $num;

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.

<?php
  class Test{
  public function index() 
  {
    return parent::index();//编译错误
  }
}

5. The money_format function

money_format is deprecated and replaced by numberFormater

6. Removed extensions

1.Firebird/Interbase

2.Recode

3.WDDX