Comparison of the differences between PHP output echo, print, print_r, printf, sprintf, and var_dump_PHP tutorial

I have been developing with .net for 5 years, and recently I suddenly wanted to get in touch with it. Things other than net, so let’s take a look at php. When learning PHP, first look at several output functions.
1. echo
echo() is not actually a function, it is a php statement, so you don’t need to use parentheses for it. 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.
Example:

Copy code The code is as follows:

$a = echo("55nav"); // Error! Cannot be used for assignment
echo "55nav"; // 55nav
echo ("55nav"); // 55nav
echo ("55nav","com"); //An error occurred, brackets cannot be used Pass multiple parameters
echo "55nav"," com"," is", " web"; // When brackets are not used, you can separate multiple values ​​with commas, and 55nav com is web will be output.
echo " 55nav is 8 good 9 web."; // Regardless of line breaks, the final display will be one line. 55nav is good web.
$fistname="55nav";
echo "$fistname com"; // If $ firstname = "55nav", then 55nav com will be output.
echo '$firstname com'; // Due to the use of single quotes, the value of $firstname will not be output, but $firstname com
?>

2. print
print() has the same usage as echo(), but the echo speed will be a little faster than print. 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(), a parsing error will occur using parentheses. 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.
Example:

Copy code The code is as follows:

$a = print("55nav"); // This is allowed
echo $a; // The value of $a is 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 value will be output. Arrays are easy to read, that is, the format corresponding to keys and values. The same is true for 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.
Example:

Copy code The code is as follows:

$a="55nav";
$c = print_r($a);
echo $c; // The value of $c is TRUE
$c = print_r($a,true);
echo $c; // The value of $c is the string 55nav
?>

4. printf function
printf The function returns a formatted string.
Syntax: printf(format,arg1,arg2,arg++)
Parameter format is the format of conversion, starting with the percent sign ("%") and ending with the conversion character. The following are possible format values:
* %% – Returns the percent sign
* %b – Binary number
* %c – Character according to the ASCII value
* %d – Signed decimal number
* %e - Continuous notation (such as 1.5e+3)
* %u - Unsigned decimal number
* %f - Floating point number (local settings aware)
* %F - Float Points (not local settings aware)
* %o – Octal number
* %s – String
* %x – Hexadecimal number (lowercase letters)
* %X – Sixteen Arguments such as base numbers (capital letters)
arg1, arg2, arg++ will be inserted into the main string at the percent sign (%) symbol. The function is executed step by step, at the first % sign, arg1 is inserted, at the second % sign, arg2 is inserted, and so on. If there are more % symbols than arg arguments, you must use placeholders. The placeholder is inserted after the % sign and consists of a number followed by "$". You can use numbers to specify the displayed parameters. See the example for details.
Example:

Copy code The code is as follows:

printf("My name is %s %s.","55nav", "com"); // My name is 55nav com.
printf("My name is %1$s %1$s","55nav", "com"); // Add 1$ or 2$ before s to indicate that the following parameters are displayed position, this line outputs My name is 55nav 55nav because only the first parameter is shown twice.
printf("My name is %2$s %1$s","55nav", "com"); // My name is com 55nav
?>

5. sprintf function
This function is used in the same way as printf. The only difference is that this function writes the formatted string into a variable instead of outputting it. .
Example:

Copy code The code is as follows:

sprintf("My name is %1$s %1$s","55nav", "com"); //You will find that nothing is output.
$out = sprintf("My name is %1$s %2$s","55nav", "com");
echo $out; //Output My name is 55nav com
? >

6. var_dump function
Function: Output the content, type of the variable or the content, type, and length of the string. Often used for debugging.

Copy code The code is as follows:

$a=100;
var_dump($ a); //int(100)
$a=100.356;
var_dump($a); //float(100.356)
?>

http://www.bkjia.com/PHPjc/327782.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/327782.htmlTechArticleI have been developing with .net for 5 years, and recently I suddenly wanted to get in touch with it. Things other than net, so let’s take a look at php. When learning PHP, first look at several output functions. 1. echo echo() Actual...