Introduction détaillée aux différences entre echo print() print_r() var_dump() en PHP lors du débogage

$arr = array('name'=> 'bob','age' => 20, 'sex' => 'man');

print_r($arr);

Array{
     [name] => bob,

     [age] => 20,

     [sex] => man
}

print_r(true);           //输出1
print_r(false);          //没有输出
print_r(null);          //没有输出

var_dump(true); //输出 bool(true)
var_dump(false);   // bool(false)
var_dump(null);   // bool(null)
var_dump(array('name' => 'bob', 'age' => 20));
array(2) {
    ['name'] => string(3) 'bob'
    ['age'] => int(20)
}

$arr=array(        
array('a'=>'aa','b'=>'bbb','c'=>'ccc'),        
array('a'=>'ddd','b'=>'eee','c'=>'fff'), 
        array('a'=>'gg','b'=>'hh')
);
echo "<pre class="brush:php;toolbar:false">";
print_r($arr);echo "

";
var_export($arr);echo "

";
var_dump($arr);echo "

Array(
    [0] => Array
        (
            [a] => aa
            [b] => bbb
            [c] => ccc
        )

    [1] => Array
        (
            [a] => ddd
            [b] => eee
            [c] => fff
        )

    [2] => Array
        (
            [a] => gg
            [b] => hh
        )

)

array (  0 => 
  array (    'a' => 'aa',    'b' => 'bbb',    'c' => 'ccc',
  ),  1 => 
  array (    'a' => 'ddd',    'b' => 'eee',    'c' => 'fff',
  ),  2 => 
  array (    'a' => 'gg',    'b' => 'hh',
  ),
)

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)

$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);echo "<pre class="brush:php;toolbar:false">";
print_r($arra);echo "

";
var_export($arra)echo "

";
var_dump($arra);echo "

[{"a":"aa","b":"bbb","c":"ccc"},{"a":"ddd","b":"eee","c":"fff"},{"a":"gg","b":"hh"}]

'[{"a":"aa","b":"bbb","c":"ccc"},{"a":"ddd","b":"eee","c":"fff"},{"a":"gg","b":"hh"}]'

string '[{"a":"aa","b":"bbb","c":"ccc"},{"a":"ddd","b":"eee","c":"fff"},{"a":"gg","b":"hh"}]' (length=84)