The difference between print_r and var_dump when testing PHP code

This article mainly introduces the difference between print_r and var_dump when testing PHP code. Interested friends can refer to it. I hope it will be helpful to everyone.

Speaking of output, I have to mention printing in php.

The first is of course the most commonly used echo, echo: output one or more strings;

print: the same as echo, but slower than echo.
print_r：
Print easy-to-understand information about the variable. If a string, integer, or float is given, the variable value itself will be printed. If an array is given, the keys and elements will be displayed in a certain format. object is similar to an array. Remember, print_r() will move the array pointer to the end. Use reset() to return the pointer to the beginning.

var_export: Similar to print_r and var_dump, but rarely used.
var_dump：
This function displays structural information about one or more expressions, including the type and value of the expression. Arrays will expand values ​​recursively, showing their structure through indentation.
The difference between var_dump and print_r:
var_dump returns the type and value of the expression while print_r only returns the result. It is easier to read than using var_dump to debug code.

The differences between print_r(), var_export() and var_dump() are as follows:

eg: Output of two-dimensional array:

$arr=array(array('a'=>'aa','b'=>'bbb','c'=>'ccc'),
           array('a'=>'ddd','b'=>'eee','c'=>'fff'),
           array('a'=>'gg','b'=>'hh'));
print_r($arr);
//print_r输出：
 //Array ( [0] => Array ( [a] => aa [b] => bbb [c] => ccc ) 
                   [1] => Array ( [a] => ddd [b] => eee [c] => fff ) 
                   [2] => Array ( [a] => gg [b] => hh ) ) 
var_export($arr);
//var_export输出：
 //array ( 0 => array ( 'a' => 'aa', 'b' => 'bbb', 'c' => 'ccc', ), 
                   1 => array ( 'a' => 'ddd', 'b' => 'eee', 'c' => 'fff', ),
                   2 => array ( 'a' => 'gg', 'b' => 'hh', ), )
var_dump($arr);
//var_dump输出：
/* array (size=3)
  0 => 
  array (size=3)
   'a' => string 'aa' (length=2)
   'b' => string 'bbb' (length=3)
   'c' => string 'ccc' (length=3)
  1 => 
  array (size=3)
           'a' => string 'ddd' (length=3)
   'b' => string 'eee' (length=3)
   'c' => string 'fff' (length=3)
  2 => 
  array (size=2)
   'a' => string 'gg' (length=2)
   'b' => string 'hh' (length=2)
*/

A json is given below Format output:

$arr=array(array('a'=>'aa','b'=>'bbb','c'=>'ccc'), 
           array('a'=>'ddd','b'=>'eee','c'=>'fff'),
           array('a'=>'gg','b'=>'hh'));
$arra=json_encode($arr);
print_r($arra);
//print_r输出：
 [{"a":"aa","b":"bbb","c":"ccc"},{"a":"ddd","b":"eee","c":"fff"},{"a":"gg","b":"hh"}]
var_export($arra);
//var_export输出：
 '[{"a":"aa","b":"bbb","c":"ccc"},{"a":"ddd","b":"eee","c":"fff"},{"a":"gg","b":"hh"}]'
var_dump($arra);
//var_dump输出：
 string '[{"a":"aa","b":"bbb","c":"ccc"},{"a":"ddd","b":"eee","c":"fff"},{"a":"gg","b":"hh"}]' (length=84)

I think everyone can understand the specific difference at a glance

Related recommendations:

php printing function introductory tutorial

Detailed introduction to PHP printing output function summary

The detailed explanation is corrected in PHP prints the error of the current page

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