What is the concatenation assignment operator in PHP? how to use?

In the previous article, we learned about the connection operators of strings. If you need it, please read "What are the connection operators of php?" 》. This time we introduce to you another operator of PHP strings. You can refer to it if you need it.

Before we learned the connection operator of strings, which is ".", now we will learn another operator of PHP strings, which is also the last operator, which is the connection assignment operator.

The basic assignment operator is "=". At first you might think it’s “equal”, but is that really the case? Let's look at a small example first. Let’s take the example from the previous article as an example and just modify the code.

<?php
$txt="世界盛大，欢迎回家！";
$offer="World grand, welcome home!";
echo $txt . $offer;
echo "<br>";
echo $txt;
echo "<br>";
echo $offer;
echo "<br>";
echo "<hr>";
echo $txt .= $offer;
echo "<br>";
echo $txt;
echo "<br>";
echo $offer;
?>

The result of this example is

We map these results to each piece of code. The first line corresponds to the connection operation introduced in the previous article. symbol, and then the second and third lines will output the original variables. The fourth line is a dividing line, there is nothing to say. The most interesting thing is here. The fifth line is the output result of using the connection assignment operator. It seems to be no different from the first line. Don’t worry, let’s continue reading. The result of the sixth line is actually the same as the result of the fifth line. Is this the difference between the connection operator and the connection assignment operator?

At the beginning of the article, we said that the assignment operator is "=", and we will think of it as "equal to", but through this small example, is this really the case?

But in fact, it's not. It actually means assigning the value of the expression on the right to the operand on the left.

When we use the connection assignment operator (.=), the value stored in our variable changes; and when we use the connection operator, the value stored in our variable does not There will be no change, which is also the biggest difference between the connection operator and the connection assignment operator.

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