Why is PHP said to be weakly typed and easy to learn? How is it different from other languages?

I want to say: "The power of Php is self-evident." There will be people here who will say that this language is the most powerful and which language is the best. The editor declares that this column does not compare which language is good or bad. This column does not compare which language is good or bad. I only focus on the nature of the PHP language, and share my experience with friends who are learning PHP like me. The editor is not a PHP expert, I am just a loyal fan of PHP. If you are interested, you can talk about PHP with me and share some of your experiences together.

Yesterday, someone replied to me and asked me what a weak type is. I emphasized it three times, but I didn’t explain it. Today, I will explain in this article what a weak type is, the benefits and disadvantages of a weak type. The reason why the editor thinks that PHP is very powerful is because PHP provides many unique features for developers to use, one of which is the PHP weak type mechanism.

Let’s look at an example first. Weak types can do the following operations:

Example 1:

<?Php
$iruohong = 1; //整数型
$iruohong = array(); //数组型
$iruohong = “iruohong.com”; //字符串型
?>

Friends who have some programming experience will use this code to understand the weak types. This is one of the manifestations of PHP's weak type mechanism. PHP kernel developers want to improve developers' development efficiency through this system that does not require declarations.

However, this mechanism will bring some troubles. For example, some of the following comparisons will bring some trouble to your developers, if the developers do not pay attention.

Example 2:

<?Php
$a = null; $b = false;
If($a == $b){
echo “a和b相等！”;
}else{
echo “a和b不相等！”;
}
?>

<?Php
$a = &#39;&#39;; $b = 0; //同样为真
If($a == $b){
echo “a和b相等！”;
}else{
echo “a和b不相等！”;
}
?>

Test it and you will find that both pieces of code will output a and b equal! , novice friends will be very surprised, how can they be equal? The editor has also suffered losses in this regard. The reason is that when you compare, PHP will not strictly check the type of the incoming variables and convert the variables freely. Because no matter whether the variable is 0 null '' or false, PHP will default to empty when comparing, and the integer value will be 0, so they are equal. If you must compare several values ​​that are different, use "===". Three equal signs represent complete equality, including equality of type and value. These are some mistakes that newbies make.

Having said so much about weak types, let’s compare the differences between strong types and weak types.

(1) Whether it is a strong type or a weak type, a variable has two attributes: type and value; that is to say, a weakly typed variable also has a type.

No matter which programming language it is, the variables used in it have both types and values. Strongly typed variable types must be clearly defined in the source code, called "variable declarations", while weakly typed variable types do not need to be declared and are interpreted by the interpreter. However, this does not mean that weakly typed variables do not have the concept of type. For example, PHP's gettype returns the "current" type of the variable.

(2) Misunderstanding: [Some people think that the type of a strongly typed variable cannot be changed, while a weak type variable can be changed as needed. Once a strongly typed variable is declared, it can only store values ​​of this type. , other values ​​must be converted before they can be assigned to the variable. There are conversions that are automatically understood by the compiler, and there are also forced conversions that are explicitly specified by the programmer. Weakly typed variable types are constantly converted as needed. 】What is inside the black brackets is a misunderstanding. Many people have this misunderstanding. In fact, neither the pre-typed variable type nor the weakly typed variable type can be changed. The following example explains everything. When assigning a value to $b, the value of $a changes, but the type of $a does not change. Please test the following example by yourself

Example 3:

<?php
$a = 25;
echo $a.&#39;|&#39;.gettype($a).&#39;<br>&#39;;
$b = $a.&#39;good&#39;;
echo $b.&#39;|&#39;.gettype($b).&#39;<br>&#39;;
echo $a.&#39;|&#39;.gettype($a).&#39;<br>&#39;;
?>

The output result is:

25|integer25good|string25|integer

(3) The forced conversion of the strongly typed language does not change the variable type

The strongly typed language has a "forced conversion", which changes the variable type The type of the value so that assignment can occur without changing the type of the variable. The type of the variable is not allowed to change.

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