What are the differences in php output?

The differences in php output are: 1. echo returns void and does not return a value; 2. echo speed is faster than print; 3. print_r function prints easy-to-understand information about variables; 4. The printf() function returns a formatted string; 5. The sprintf function writes the formatted string into a variable instead of outputting it; 6. The var_dump function is used for debugging.

The operating environment of this tutorial: windows7 system, PHP8.1 version, DELL G3 computer

The six output methods in php Difference

php output echo, print , print_r , printf , Comparison of the differences between sprintf and var_dump.

1. echo

echo() is actually not a function, but a php statement, so you don’t need to It uses parentheses. However, if you wish to pass more than one argument to echo(), then using parentheses will cause a parsing error. Moreover, echo returns void and does not return a value, so it cannot be used to assign values.

<?php

$a = echo("words"); // 错误！不能用来赋值

echo "words"; // 55nav

echo ("words"); // 55nav

echo ("apple","bear"); //发生错误，有括号不能传递多个参数

echo "alice","bill","cart", "daring";  // 不用括号的时候可以用逗号隔开多个值， 会输出 alicebillcartdaring  不管是否换行，最终显示都是为一行

$fistname="alice";

echo "$fistname com"; // 如果 $firstname = "alice", 则会输出 alice com.

echo &#39;$firstname com&#39;; // 由于使用单引号，所以不会输出$firstname的值，而是输出 $firstname com

?>

2、print

print() has the same usage as echo(), but echo is faster than print A little faster. It's actually not a function either, so you don't need to use parentheses on it.

However, if you wish to pass more than one argument to print(), then using parentheses will cause a parsing error.

Note that print always returns 1, which is different from echo.

That is, you can use print to assign values, but it has no practical meaning. .

1 <?php 
2 
3 $a = print("alice"); // 这个是允许的
4 
5 echo $a; // $a的值是1

#3. print_r function

The print_r function prints easy-to-understand information about variables.

Syntax:

mixed print_r ( mixed $expression [, bool return ] )

If the variable is string, integer or float, its value will be output directly. If the variable is an array, a formatted array will be output for easy reading, that is, the format corresponding to key and value.

Similar to object objects.

print_r has two parameters. The first is a variable and the second can be set to true. If set to true, a string will be returned, otherwise a Boolean value TRUE## will be returned. #.

<?php

$a="alice";

$c = print_r($a);

echo $c;  // $c的值是TRUE

$c = print_r($a,true);

echo $c; // $c的值是字符串alice

$d = [1,2,3,4];

print_r($d); // Array ( [0] => 1 [1] => 2 [2] => 3 [3] => 4 )

4. printf function

printf() function returns a formatted string .

Syntax:

printf(format,arg1,arg2,arg)

Parameter format It is the conversion format, starting with the percent sign ("%") and ending with the conversion character.

The following are possible format values: * %% – Returns the percent sign

* %b – 二进制数* %c – 依照 ASCII 值的字符* %d – 带符号十进制数* %e – 可续计数法（比如 1.5e+3）* %u – 无符号十进制数* %f – 浮点数(local settings aware)* %F – 浮点数(not local settings aware)* %o – 八进制数* %s – 字符串* %x – 十六进制数（小写字母）* %X – 十六进制数（大写字母）arg1, arg2, arg++ 等参数将插入到主字符串中的百分号 (%) 符号处。该函数是逐步执行的，在第一个 % 符号中，插入 arg1，在第二个 % 符号处，插入 arg2，依此类推。

If there are more than % signs arg parameter, you must use placeholders. Placeholders are inserted after the % sign and consist of numbers and "\$".

You can use numbers to specify the displayed parameters. Please see the example for details.

<?php

printf("My name is %s %s。","alice", "com"); // My name is alice com。

printf("My name is %1\$s %1\$s","alice", "com"); // 在s前添加1\$或2\$.....表示后面的参数显示的位置，此行输出 My name is alice alice因为只显示第一个参数两次。

printf("My name is %2\$s %1\$s","alice", "com"); // My name is com alice

?>

5、sprintf函数

此函数使用方法和printf一样，唯一不同的就是该函数把格式化的字符串写入一个变量中，而不是输出来。

<?php

sprintf("My name is %1\$s %1\$s","alice", "com");  //你会发现没有任何东西输出的。

$out = sprintf("My name is %1\$s %2\$s","alice", "com");

echo $out;  //输出 My name is alice com

6、var_dump函数

功能: 输出变量的内容、类型或字符串的内容、类型、长度。常用来调试。

1 var_dump('hello'); // string(5) "hello"

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