Detailed explanation of php echo output string function

echo "asd";//字符串 
echo "ads$c";//字符串+变量 
echo 'ads$c';//字符串 asd$c $c不是变量 
echo "sd"."vs"; 
echo "sd","vs"; 
echo $a; 
echo $a.$b; 
echo $a,$b; 
echo $a.$b.$c; 
echo $a,$b,$c; 
echo "kaskd{$c}asd"; 
echo "kakskd{$arr['lo']}"; 
echo "kakskd{$obj->a}"; 
echo "kaskd".$c."kasd"; 
echo "kaskd".$arr['lo']."kasd"; 
echo "kaskd".$obj->a."kasd"; 
echo "kaskd".func($c)."kasd"; 
echo "kaksk".($a+1)."dkkasd"; 
echo $c."jaksd"; 
echo $c,"jaksd"; 
//php多行输出方法 
echo <<<END 
This uses the "here document" syntax to output 
END; 
//输出简写 
<?php echo $a;?> 　　<?=$a?>

<?php 
echo "Hello World"; 

echo "This spans 
multiple lines. The newlines will be 
output as well"; 

echo "This spans\nmultiple lines. The newlines will be\noutput as well."; 

echo "Escaping characters is done \"Like this\"."; 

// You can use variables inside of an echo statement 
$foo = "foobar"; 
$bar = "barbaz"; 

echo "foo is $foo"; // foo is foobar 

// You can also use arrays 
$baz = array("value" => "foo"); 

echo "this is {$baz[&#39;value&#39;]} !"; // this is foo ! 

// Using single quotes will print the variable name, not the value 
echo &#39;foo is $foo&#39;; // foo is $foo 

// If you are not using any other characters, you can just echo variables 
echo $foo; // foobar 
echo $foo,$bar; // foobarbarbaz 

// Some people prefer passing multiple parameters to echo over concatenation. 
echo &#39;This &#39;, &#39;string &#39;, &#39;was &#39;, &#39;made &#39;, &#39;with multiple parameters.&#39;, chr(10); 
echo &#39;This &#39; . &#39;string &#39; . &#39;was &#39; . &#39;made &#39; . &#39;with concatenation.&#39; . "\n"; 

echo <<<END 
This uses the "here document" syntax to output 
multiple lines with $variable interpolation. Note 
that the here document terminator must appear on a 
line with just a semicolon. no extra whitespace! 
END; 

// Because echo does not behave like a function, the following code is invalid. 
($some_var) ? echo &#39;true&#39; : echo &#39;false&#39;; 

// However, the following examples will work: 
($some_var) ? print &#39;true&#39; : print &#39;false&#39;; // print is also a construct, but 
// it behaves like a function, so 
// it may be used in this context. 
echo $some_var ? &#39;true&#39;: &#39;false&#39;; // changing the statement around 
?>

The following is the official manual description:
Definition and Usage
Definition and Usage
The echo() function outputs one or more strings.
The echo() function outputs one or more strings. Multiple strings.
Syntax
Syntax
echo(strings)
Parameter Parameter Description
strings Required. One or more strings to be sent to the output
Required parameters. Specify one or more strings that need to be sent to the results
Tips and Notes
Tips and Notes
Note: The echo() function is not actually a function, so you are not required to use parentheses with it. However, if you want to pass more than one parameter to echo(), using parentheses will generate a parse error.
Note: The echo() function is not a real function, so you don’t have to Go use it. If you want to pass more than one argument to the echo() function, then using parentheses "()" will generate an error.
Tip: The echo() function is slightly faster than print().
Tip: The echo() function is equivalent to a simplified version of the print() function.
Tip: The echo() function has the following shortcut syntax. See example 5.
Tip: The echo() function has the following shortcut syntax. For details, see: Case 5.
Example 1
Case 1

<?php 
$str = "Who&#39;s Kai Jim?"; 
echo $str; 
echo "<br />"; 
echo $str."<br />I don&#39;t know!"; 
?>

The output of the code above will be:
The above code will output the following results:
Who's Kai Jim?Who's Kai Jim?I don 't know!

Example 2
Case 2

<?php 
echo "This textspans multiplelines."; 
?>

The output of the code above will be:
The above code will output the following results:
This text spans multiple lines.

Example 3
Case 3

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

The output of the code above will be:
The above code will output the following result:
This string was made with multiple parameters

Example 4
Case 4
Difference of single and double quotes. Single quotes will print the variable name, not the value:
Difference between single quotes (') and double quotes ("). Single quotes will output the variable name instead of the variable value:

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

The output of the code above will be:
The above code will output the following result:
Roses are redRoses are $color

Example 5
Case 5
Shortcut syntax:
Abbreviation (shortcut) syntax:

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

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