Summary of PHP printout functions

This article summarizes and introduces 7 commonly used print output functions in PHP, namely echo, print, printf, sprintf, print_r, var_dump, and die. I hope it will be helpful for everyone to learn PHP.

Development You must debug the code, and PHP debugging code cannot be single-step debugged through development software such as Xcode like the iOS compiler language. Therefore, PHP developers usually print relevant prompt information through output functions to debug the code.

A step-by-step explanation of commonly used print output functions in PHP

echo

The echo function can output multiple strings at the same time, with Multiple parameters, but parentheses are not required and there is no return value. However, there is no problem if you bring parentheses, so the function requires parentheses:

echo &#39;PHP中文网<br>&#39;;
echo (&#39;echo也可以带括号<br>&#39;);

I believe the echo function is the most commonly used printing function!

print

The print function can only output one string at a time, can only take one parameter, requires parentheses and will have a return value. Returns false when its execution fails.

print(&#39;www.php.cn<br>&#39;);

The print function is also used quite a lot, for printing information, but it is not as convenient as echo, but it has its uses!

printf

The printf function takes two parameters. The first parameter specifies the output format, and the second parameter is the variable to be output. The output format is:

%s: by string;
%d: by integer;
%b: by binary;
%x: by hexadecimal;
%o: By octal;
$f: By floating point

/*
$var = 10;
printf(&#39;整型：%d<br>&#39;, $var);
printf(&#39;浮点型：%.2f<br>&#39;, $var); // 保留两位小数
printf(&#39;字符串：%s<br>&#39;, $var);
printf(&#39;二进制：%b<br>&#39;, $var);
printf(&#39;八进制：%o<br>&#39;, $var);
printf(&#39;十六进制：%x<br>&#39;, $var);
 
// 打印结果
/*
整型：10
浮点型：10.00
字符串：10
二进制：1010
八进制：12
十六进制：a
*/

sprintf

sprintf cannot directly output the variable value, but directly The value is read into the specified variable:

$ret = sprintf('%.2f', $var);
echo "结果：{$ret}<br>";

This function is very useful for formatting variable output and is used a lot!

print_r

print_r This function is used to output an array, with one or two. If parameter two is set to YES, the expression information will not be output, but will be returned directly:

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

$arr = array('name' => 'PHP中文网', 'site' => 'www.php.cn');
print_r($arr);
echo &#39;<br>&#39;;
 
// 参数二设置为true则不会打印，而是直接返回
$arr1 = print_r($arr, true);
echo "{$arr1}<br>";

var_dump

var_dump This function is used the most during the debugging process. It is used to output the content, type, and string content of variables. , often used for debugging in development:

// 当打印的是字符串，其中有对象时，打印出来是：
// string(20) "var_dump：Array
var_dump(&#39;var_dump：&#39; . $arr . &#39;<br>&#39;);
 
// 当只有对象本身时，打印出来如下：
// " array(2) { ["name"]=> string(21) "PHP中文网" ["site"]=> string(19) "www.php.cn" }
var_dump($arr);

die

die function is also widely used. During the debugging process, the following execution is often interrupted. , it will output the content first, and then exit the program or not output the content:

if (!isset($type)) {
 die(&#39;I am die!<br>&#39;);
}

Summary:

The above functions can print object values, system function values ​​and arrays content;
echo, print, and printf can print variable contents, but cannot display arrays and system super variable arrays;
print_r and var_dump can not only print arrays and scalar variables, but also print the contents of objects;
The var_dump statement can not only print the contents of variables and arrays, but also display the contents of Boolean variables and resources;
The var_export function returns structural information about the variables passed to the function, which is similar to the var_dump() function, except that The content returned is legal php code.

The above is a summary of all the printout functions in PHP introduced in this article. I hope you will like it

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