这太简单了。var_dump()函数显示关于变量/表达式的结构化信息，包括其类型和值。而print_r()以人类可读的方式显示关于变量的信息。

示例:假设我们有以下数组，我们想显示它的内容。

$arr = array ('xyz', false, true, 99, array('50'));

print_r()函数-显示人类可读的输出

Array
(
    [0] => xyz
    [1] =>
    [2] => 1
    [3] => 99
    [4] => Array
        (
            [0] => 50
        )
)

var_dump()函数-显示值和类型

array(5) {
  [0]=>
  string(3) "xyz"
  [1]=>
  bool(false)
  [2]=>
  bool(true)
  [3]=>
  int(100)
  [4]=>
  array(1) {
    [0]=>
    string(2) "50"
  }
}

详情请访问:https://stackhowto.com/how-to-display-php-variable-values-with-echo-print_r-and-var_dump/

Var_dump()将向您显示对象的类型以及其中的内容。

你会得到=> (string)示例如下。

Print_r()只输出内容。

示例如下:

对于所有需要var_dump()函数进行测试的人!

I've written my own test dump function, cause i didn't whant to do that ob_start ... stuff over and over again. The nice thing, it even get's the parameter names from source!

function test_dump (...$params)
{
    
    $file_test_dump = 'test_dump.log';

    $backtrace = debug_backtrace(0, 3);

    $caller_file        = $backtrace[0]['file']);  
    $caller_function    = $backtrace[1]['function'];
    $caller_line        = $backtrace[0]['line'];

    if (empty($params))
    {
        file_put_contents ($file_test_dump, "!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!\n" , FILE_APPEND);
        file_put_contents ($file_test_dump, '!!!!!! ' . date ("[Y-m-d H:i:s:u]", time()) . " - FILE: {$caller_file} | FUNCTION: {$caller_function} | LINE: {$caller_line} !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! \n\n" , FILE_APPEND);
        file_put_contents ($file_test_dump, "!!! No parameter given !!! \n\n" , FILE_APPEND);
        return;
    }
    
    

    // --- get source file ---
    $source_file = file($backtrace[0]['file']);
    
    // --- get line of source file and pre filter with regex ---
    preg_match ('~\(([^*]*)\)~', $source_file [intval($backtrace[0]['line']) - 1], $parameter_line);
    $parameter_line_filtered = str_replace(" ", "", $parameter_line [1]);

    // put parameter names into array
    $params_names = explode(',', $parameter_line_filtered);



    // --- OUTPUT   ----
    
    file_put_contents ($file_test_dump, "#######################################################################################################################################################################################################################\n" , FILE_APPEND);
    file_put_contents ($file_test_dump, '### ' . date ("[Y-m-d H:i:s:u]", time()) . " - FILE: {$caller_file} | FUNCTION: {$caller_function} | LINE: {$caller_line} ### \n\n" , FILE_APPEND);
    
    
    $i = 0;
    
    foreach ($params as $param)
    {

        $i++;

        file_put_contents ($file_test_dump, "   --- Parameter " . $i . ': ' . $params_names[$i - 1] . " --------------------------------------------------------------------------------------------------------------------------\n", FILE_APPEND);

        if (    is_array($param)    ||
                is_object($param) ||
                is_bool($param) )
        {
            ob_start();
            var_dump($param);
            file_put_contents ($file_test_dump, ob_get_contents() . "\n\n", FILE_APPEND);
            ob_end_clean();
        }
        else
        {
            file_put_contents ($file_test_dump, $param . "\n\n", FILE_APPEND);
        }


    }

    file_put_contents ($file_test_dump, "\n\n", FILE_APPEND);

}

通常，print_r()输出更好，更简洁，更容易阅读，也就是更易于人类阅读，但不能显示数据类型。

使用print_r()，你也可以将输出存储到一个变量中:

$output = print_r($array, true);

这是var_dump()无法做到的。然而var_dump()可以显示数据类型。

对于大型数组，print_r显示的信息可能远远超出有用的范围。您可以像这样截断它，显示前2000个字符或任何您需要的字符。

  echo "<pre>" . substr(print_r($dataset, 1), 0, 2000) . "</pre>";

print_r()和var_dump()是PHP中用于调试目的的数组调试函数。print_r()函数返回数组键及其成员为array ([key] = value)，而var_dump()函数返回数组列表及其数据类型和长度的数组键，例如array (array_length){[0] = string(1)'a'}。