PHP outputs one or more string functions echo

Definition and usage

echo() function outputs one or more strings.

Note: The echo() function is not actually a function, so you don't have to use parentheses with it. However, if you want to pass more than one argument to echo(), using parentheses will generate a parsing error.

Tip: The echo() function is slightly faster than print().

Tip: The echo() function also has simplified syntax. Prior to PHP 5.4.0, this syntax only worked if the short_open_tag configuration setting was enabled.

Grammar

echo(strings)

We all know that commas can be used to connect strings in .echo. And after testing, this method of connecting strings is better than directly using The dot number should be fast. 12

For example:

echo 'abc'.'def'; //Use the dot number to connect the string echo 'abc','def'; / /Use commas to connect strings 12
Maybe many people know that commas are faster than periods. But they don’t know why. Let alone what the difference between the two is.
Then let’s give some examples. Recognize the difference between them before. 123

echo '1+5=' . 1+5;1

Look at the above. The output result is 6.. instead of 1+5=6. It’s a bit magical, right?
What’s even more magical is you Look at the example below. 123

echo '1+5=' . 5+1;  //输出2结果 1

is very strange. We see that we change the positions of 5 and 1. The result becomes 2.
Why is this? Is it in PHP There is no commutative property in addition? Of course not..
Let’s not think about why. If I replace the period above with a comma and try it.12345

echo '1+5=' , 5+1;    //输出 1+5=6echo '1+5=' , 1+5;    //输出 1+5=612

It can be seen that only Only by using commas can we get the expected results.
Then why doesn't the period work? Why does the comma work? 123

echo ('1+5' . 5)+1; //输出2 1

The result we get after adding parentheses to the previous one. It's the same.
It proves that PHP concatenates the strings first and then performs the addition calculation. It proceeds from left to right.
That's good. Since the strings are concatenated first, then it should be "1 +55". Then add 1 to this string. Then why is 2 output?
This is related to the mechanism of converting strings into numbers in PHP. Let's look at the following example 123456

echo (int)'abc1';   //输出0echo (int)'1abc'; //输出1echo (int)'2abc'; //输出2echo (int)'22abc'; //输出221234

We can see from the above example that if a string is forced to be converted into a number, PHP will search for the beginning of the string. If the beginning is a number, it will be converted. If not, it will be returned directly. 0.
Go back to 1+55. Since this string is 1+55, it should be 1 after forced type conversion. Add 1 to this. Of course it is 2.
To prove Our conjecture. Let’s verify it. 1234

echo '5+1=' . 1+5; //输出10echo '5+1=' . 5+1; //输出6echo '1+5=' . 1+5; //输出6echo '1+5=' . 5+1; //输出21234

The results prove that our assumption is correct.
So why does using commas eliminate the above problems?
** The manual says that using commas means multiple parameters. In other words, it is multiple parameters. In other words, commas separated are equivalent to N parameters. In other words, echo is used as a function. In this case, echo will

Parameters Description

strings Required. One or more strings to send to the output.

Technical details Return value:

Example 1

Output the value of the string variable ($str):

<?php
$str = "Hello world!";
echo $str;
?>

Example 2

Output the value of the string variable ($str), including HTML tags:

<?php
$str = "Hello world!";
echo $str;
echo "<br>What a nice day!";
?>

Example 3

Connect two string variables:

<?php
$str1="Hello world!";
$str2="What a nice day!";
echo $str1 . " " . $str2;
?>

Example 4

Output the value of the array:

<?php
$age=array("Peter"=>"35");
echo "Peter is " . $age[&#39;Peter&#39;] . " years old.";
?>

Example 5

Output some text:

<?php
echo "This text
spans multiple
lines.";
?>

Example 6

How to use Multiple parameters:

<?php
echo &#39;This &#39;,&#39;string &#39;,&#39;was &#39;,&#39;made &#39;,&#39;with multiple parameters.&#39;;
?>

Example 7

The difference between single quotes and double quotes. Single quotes will output the variable name, not the value:

<?php
$color = "red";
echo "Roses are $color";
echo "<br>";
echo &#39;Roses are $color&#39;;
?>

Example 8

Simplified syntax (only applicable if the short_open_tag configuration setting is enabled):

<?php
$color = "red";
?>
<p>Roses are <?=$color?></p>

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