The difference between echo and print in PHP, phpechoprint_PHP tutorial

The difference between echo and print in PHP, phpechoprint

Generally speaking, dynamic output of HTML content in PHP is achieved through print and echo statements. In actual use, the functions of print and echo are almost exactly the same. It can be said that wherever one can be used, the other can also be used. However, there is still a very important difference between the two: in the echo function, multiple strings can be output at the same time, while in the print function, only one string can be output at the same time. At the same time, the echo function does not require parentheses, so the echo function is more like a statement than a function.
Neither echo nor print are functions, but language constructs, so parentheses are not necessary.

Their difference is:

(1) echo can output multiple strings , like the following:

echo 'a','b','c';

If you insist on adding parentheses, please note that writing echo ('a','b','c'); is wrong. It should be written as:

echo ('a'),('b'),('c');

It has no function-like behavior, so it cannot be used in the context of a function
(2) print can only output a string, it can behave like a function , for example, you can use it as follows:

$ret = print 'Hello World';

So it can be used in more complex expressions.
In addition, echo is relatively efficient!

Look at the following code:

<&#63;php
$a='hello ';$b='php world!';echo $a,$b.'<br />';//echo 可以用逗号分隔字符串变量来显示
print $a.$b.'<br />';//而print不能使用逗号，只能用点号分隔，
//print $a,$b.'<br />';//这里使用逗号时报错。
&#63;>

Analysis summary:

echo command is the same as print command, there is no difference
There is a difference between the echo function and the print function.
echo() No return value, same as echo command
print() has a return value, if successful, it returns 1, if false, it returns 0.
printf() is similar to sprintf(), both formatted output. The difference is that the former outputs to standard output, and the latter outputs to variable

looks like:

echo  <<< EOT 
EOT; 
print  <<< EOT 
EOT; 

The writing format of

has the following meaning:

633aa0b0b17142e2cce1bbc7342c8481
#Results======
Hello world. Day number 123

If there are more % symbols than arg parameters, then you must use placeholders. Placeholders are inserted after the % sign and consist of numbers and "\$". See example 3.
Example: ?php

$number = 123;

printf("With 2 decimals: %1\$.2fbr />With no decimals: %1\$u" ,$number);

?>
#Result
With 2 decimals: 123.00
With no decimals: 123

print_r() and var_dump()
print_r() can simply print out strings and numbers, while arrays are displayed as a bracketed list of keys and values, starting with Array. For example, $a = array('name' => 'Fred', 'age' => '15', 'wife' => 'Wilma');

print_r($a);
Output: Array

{

[name] => Fred

[age] => 15

[wife] => ; The same goes for Wilma

}
objects. For example, class P {

var $name = 'nat';

// ...

}

$p = new P;

print_r($p);
Output: Object

{

[name] => nat

}
but print_r( ) The results of outputting Boolean values ​​and NULL are meaningless, because they all print "...the rest of the full text>>

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