About the difference between var_export, print_r and var_dump in debugging in PHP

This article mainly introduces the differences between var_export, print_r, and var_dump debugging in PHP. It is very good and has certain reference value. Friends in need can refer to it

1. output basic type

Code

$n = "test";
var_export($n);
print_r($n);
var_dump($n);
echo &#39;-----------------&#39; . &#39;<br/><br/>&#39;;
file_put_contents("index.log", var_export($n, true) . PHP_EOL, FILE_APPEND);
file_put_contents("index.log", print_r($n, true) . PHP_EOL, FILE_APPEND);
file_put_contents("index.log", var_dump($n) . PHP_EOL, FILE_APPEND);

Result

(1) Front end:

'test' test /Users/xjnotxj/Program/PhpstormProject/colin/index.php:9:string 'test' (length=4) ----------------- /Users /xjnotxj/Program/PhpstormProject/colin/index.php:15:string 'test' (length=4)

(2)index.log：

'test' test

2, output array

code

$arr = array(
  "a" => 1,
  "b" => "222",
  "c" => 3,
);
var_export($arr);
print_r($arr);
var_dump($arr);
echo &#39;-----------------&#39; . &#39;<br/><br/>&#39;;
file_put_contents("index.log", var_export($arr, true) . PHP_EOL, FILE_APPEND);
file_put_contents("index.log", print_r($arr, true) . PHP_EOL, FILE_APPEND);
file_put_contents("index.log", var_dump($arr) . PHP_EOL, FILE_APPEND);

result

（ 1) Front end:

array ( 'a' => 1, 'b' => '222', 'c' => 3, ) Array ( [a] => 1 [b] => 222 [c] => 3 ) /Users/xjnotxj/Program/PhpstormProject/colin/index.php:13: array (size=3) 'a' => int 1 'b' => string '222' (length=3) 'c' => int 3 ----------------- /Users/xjnotxj/Program/PhpstormProject/colin/index. php:19: array (size=3) 'a' => int 1 'b' => string '222' (length=3) 'c' => int 3

(2) index.log:

array ( 'a' => 1, 'b' => '222', 'c' => 3, ) Array ( [a] => 1 [b] => 222 [c] => 3 )

3, output object

code

class foo
{
  public $n;
  public function do_foo()
  {
    echo "Doing foo." . $this->n;
  }
}
$object = new foo;
var_export($object);
print_r($object);
var_dump($object);
echo &#39;-----------------&#39; . &#39;<br/><br/>&#39;;
file_put_contents("index.log", var_export($object, true) . PHP_EOL, FILE_APPEND);
file_put_contents("index.log", print_r($object, true) . PHP_EOL, FILE_APPEND);
file_put_contents("index.log", var_dump($object) . PHP_EOL, FILE_APPEND);

Result

(1) Front end:

foo::__set_state(array( 'n' => NULL, ))
foo Object ([n] => )
/Users/xjnotxj/Program/PhpstormProject/colin/index.php:19: object(foo)[1] public 'n' => null -- --------------- /Users/xjnotxj/Program/PhpstormProject/colin/index.php:25: object(foo)[1] public 'n' => null

(2) index.log:

foo::__set_state(array( 'n' => NULL, )) foo Object ( [n] => )

##Summary:

1. Detailed output results: var_export ≈ print_r < var_dump

2. When debugging, when calling var_export, print_r, var_dump, there is no need to add echo in front.

3. If the second parameter of var_export and print_r is true, the value will be returned. var_dump does not support , so do not use var_dump when using file_put_contents to output debugging.

4. It is recommended to use var_dump directly for debugging in the development environment to obtain detailed debugging information and code line positioning; to use var_export or print_r for debugging in the production environment. Remember to set the second parameter to true to return output. value instead of outputting it directly to the front-end influence line.

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