powerpoint2003 official download PHP learning output string echo, print, printf, print_r and var_dump

They are introduced one by one below.
1. echo
echo is a keyword in PHP, it has no return value. In terms of writing, it can omit the parentheses. The following code:

Copy the code The code is as follows:

echo 'Test String';
echo('Test String');

2. print
print is also a keyword of PHP, it has return Value, generally returns true, there should be no case of returning false. In terms of writing, it is the same as echo, and the parentheses can be omitted. The following code:

Copy the code The code is as follows:

print 'Test String';
print('Test String');

3. printf
printf can be formatted like printf in C language Output a string. Its format is similar to that of C language, both starting with %. Its specifier is defined below.
b The parameter is an integer, display its binary number
c The parameter is an integer, display the corresponding ASCII character
d The parameter is an integer, display its decimal number
f The parameter is double precision, display it as a floating point number
e The parameter is double precision, display it in scientific notation The type
g parameter is a double precision, displayed as a floating point number or scientific notation
o The parameter is an integer, displayed as an octal number
s The parameter is a string, displayed as a string
u The parameter is an unsigned integer, displayed as a decimal
x/ The parameter , if the rounded value is less than 1000000, it will be output directly, and if it is greater than 1000000, it will be displayed in scientific notation. When the value of f is greater than 1.2e23, the output result is incorrect.
Except for %, all of the above can specify the total number of output digits (the decimal point and E count as one), and you can specify 0 or a space as the complement character, and you can also specify whether the complement is on the left or right.
f, e can specify the number of digits after the decimal point.
For example, %5d means that the total number of output digits is 5, and the remaining digits are left filled with spaces; %05d means that the total number of output digits is 5, and the remaining digits are left filled with 0s; %05.1f means that the total number of output digits is 5, and the remaining digits are left filled with 0s and 0s after the decimal point 1 digit; %-05.1f means that the total number of output digits is 5, and any missing digits are padded with 0 on the right and 1 digit after the decimal point;
Sample code:

Copy code The code is as follows:

printf("%7.2f" , 1.2); // " 1.20"

printf("%-07.2f", 1.2); // "1.20000"


4. sprintf

sprintf is the same as format conversion and printf. The difference between the two is that printf outputs directly. And sprintf returns a formatted string.
5. print_r and var_dump
Both print_r and var_dump can output arrays and objects, but print_r’s output of Boolean types is not obvious; var_dump’s output is more detailed and is generally used during debugging.
The following code:

Copy the code The code is as follows:

$v = new test();

print_r($v);
var_dump($v);
class test {
public $num = 1 ;
public $str = "222";
public $bln = true;


The result is:

Copy the code The code is as follows:

test Object

(
[num] => 1
[str] => 222
[bool] => 1
)
object(test)#1 (3) {
["num"]=>
int(1)
["str"]=> ;
string(3) "222"
["bool"]=>
bool(true)
}


Reference:

PHP Programming, 2003, Chapter 4 String, Output String
The above introduces the output strings echo, print, printf, print_r and var_dump of powerpoint2003 official download PHP learning, including the content of powerpoint2003 official download. I hope it will be helpful to friends who are interested in PHP tutorials.