This article is the PHP output echo, print, Print_r, printf, sprintf, var_dump the difference between the detailed analysis of the introduction, the need for a friend reference With. NET development has been 5 years, and recently suddenly want to touch. NET, so I'll take a look at PHP. In learning PHP first look at several output functions.
First, Echo
Echo () is not actually a function, it is a PHP statement, so you do not need to use parentheses on it. However, if you want to pass more than one argument to Echo (), a parse error occurs when you use parentheses. and echo returns void and does not return a value, so it cannot be used to assign a value.
Example:
Copy CodeThe code is as follows:
<?php
$a = Echo ("55nav"); Error! Cannot be used to assign a value
echo "55nav"; 55nav
Echo ("55nav"); 55nav
Echo ("55nav", "com"); An error occurred with parentheses that cannot pass multiple arguments
echo "55nav", "com", "is", "web"; You can separate multiple values with commas without parentheses, and output a 55nav COM is web
echo "55nav is 8 good 9 web."; The final display is for a row of 55nav is good web, regardless of whether the line is wrapped.
$fistname = "55nav";
echo "$fistname com"; If $firstname = "55nav", 55nav com is output.
echo ' $firstname com '; Because the single quotation marks are used, the $firstname value is not output, but the output $firstname com
?>
Second, print
Print () is the same as Echo (), but the echo speed is a little bit faster than print. It is not actually a function, so you do not need to use parentheses on it. However, if you want to pass more than one parameter to print (), a parse error occurs when you use parentheses. Note that print always returns 1, which is different from Echo, which means you can use print to assign a value, but it doesn't make sense.
Example:
Copy CodeThe code is as follows:
<?php
$a = print ("55nav"); This is permissible.
echo $a; The value of $a is 1
?>
Three, 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 a string, the integer or float will output its value directly, and if the variable is an array, it will output a formatted array for readability, which is the format of the key and value. Similar for object objects. Print_r has two parameters, the first is a variable, the second can be set to true, and if set to True, returns a string, otherwise returns a Boolean value of true.
Example:
Copy CodeThe code is as follows:
<?php
$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
?>
Four, printf function
The printf function returns a formatted string.
Syntax: printf (format,arg1,arg2,arg++)
The parameters format is the converted format, starting with the percent sign ("%") to the end of the converted character. The following is the possible format value:
*%%– return percent symbol
*%b– binary number
*%c– characters in accordance with ASCII values
*%d– Signed decimal number
*%e– counting method (e.g. 1.5e+3)
*%u– unsigned decimal number
*%f– floating point (Local settings Aware)
*%f– floating point number (not local settings aware)
*%o– octal number
*%s– String
*%x– hexadecimal number (lowercase letter)
*%x– hexadecimal number (capital letter)
Arg1, arg2, arg++, etc. parameters will be inserted into the main string percent percent (%) Symbol. The function is executed incrementally, in the first% symbol, insert arg1, insert arg2 at the second% symbol, and so on. If the% symbol is more than the arg parameter, you must use a placeholder. After the placeholder is inserted in the% symbol, it consists of a number and a "\$". You can use numbers to specify the parameters that are displayed, see examples for details.
Example:
Copy CodeThe code is as follows:
<?php
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\$ in front of s ..... Represents the position of the following parameter display, this line outputs My name is 55nav 55nav because only the first parameter is displayed two times.
printf ("My name is%2\ $s%1\ $s", "55nav", "com"); My name is COM 55nav
?>
Five, sprintf function
This function uses the same method as printf, except that the function writes the formatted string to a variable instead of the output.
Example:
Copy CodeThe code is as follows:
<?php
sprintf ("My name is%1\ $s%1\ $s", "55nav", "com"); You will find nothing to output.
$out = sprintf ("My name is%1\ $s%2\ $s", "55nav", "com");
Echo $out; Output My name is 55nav com
?>
vi.. Var_dump function
Function: The content, type, and length of the output variable's contents, type, or string. Commonly used to debug.
Copy CodeThe code is as follows:
<?php
$a = 100;
Var_dump ($a); Int (100)
$a = 100.356;
Var_dump ($a); Float (100.356)
?>
The difference between the PHP output echo, print, Print_r, printf, sprintf, Var_dump
