Usage examples of PHP string concatenation

Many times we need to connect several strings for display. In PHP, strings are connected using "dots", which is the half-width period in English. " . " . " . " is a string concatenation operator that can link two or more strings into one string. For example:

<?php
$name = "PHP中文网：";
$url =  "www.php";
echo $name . $url . ".cn";
?>

The output result is:

PHP中文网： www.php.cn

There is no way to connect a large number of strings using the string connection symbol. PHP allows programmers to directly include it in double quotes String Variable, when double quotes (" ") are used after the echo statement, the following format can be used to achieve the same effect. For example:

<?php
$name = "PHP中文网：";
$url =  "www.php";
echo "$name$url.cn";     // 双引号里的变量同一般的字符串自动进行区分
?>

The output result is:

PHP中文网：www.php.cn

String echo output comma can also be used as a php connector

Output When there are multiple strings, use commas instead of periods to separate the strings, which is faster. The following 4 methods can all get the same result, but only the 4th method is the best.

<?php
$foo = &#39;Tom&#39;;
echo "Hello $foo, welcome to phpcn.";
echo "<br>";
echo "Hello " . $foo . " welcome to phpcn.";
echo "<br>";
echo &#39;Hello &#39; . $foo . &#39; welcome to phpcn.&#39;;
echo "<br>";
echo &#39;Hello &#39;, $foo , &#39; welcome to phpcn.&#39;;
?>

Note:

The first comma " , " cannot be run because using double quotes will force PHP to find a replacement value for this string.

The second one is better because there is no replacement that needs to be executed in PHP.

The third one is better because it uses single quotes, so the language knows that you can send text out of the process, but the "bad" thing is the use of the concatenation character (doesn't work, just like the second example) ).

The last one uses single quotes and adds a connection character. Why is this the best way to handle it?

Let's look at the third case first. PHP creates a string containing "Hello", then expands it and adds the foo variable ("Tom"), and then expands it again and adds "welcome" to phpcn." statement, then echo can use it.

However, in the fourth case, the only thing echo does is to send "Hello", then output the contents of $foo, and then output "welcome to phpcn.". Because echo only sends text and does not create a string that needs to be expanded.

At this point, you should understand that optimizing the php string connector can improve the running speed of the program. And I found that the "," comma can also be used as a connector in php. Usually everyone uses a little "." as a connector. Doesn't it feel amazing?

It is said that this may be a habit brought over from C. Outputs such as printf are variable parameters, and echo has also inherited this fine tradition. But what needs to be understood is that the comma here is the parameter separator, not the string concatenation character.

Let’s talk about the difference between commas and periods

echo $str,$str2,$str3;

Using commas to perform operations is to output the operation results one by one

And

echo $str.$str2.$str3;

Using dots is to first Perform operations on all strings to get the results and then output them.

Looking at it this way, of course the comma is more efficient than the period. Because comma concatenation does not require operation.

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