print_r


php128 apg

PRINTS human-readable information about a variable.



<?php

 mix print_r ( mix $expression [, bool $return = FALSE ] )

where,

$expression = The expression to be printed

$return = To control if the information will be printed or not
                 ( SEE the below TABLE )

?>



This function returns human-readable information about a variable and, specially designed to print ARRAYS and/or OBJECTS.


ARRAYS, RESOURCES and OBJECTS ...

... will be studied in more detail ...


... in a special chapter of this tutorial



 $expression 


The expression to be printed.



$return

VALUE WHAT DOES
FALSE The information will be printed
TRUE The information will not be printed
ed48


  1 EXERCISE   

<?php

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  
      SOME USER-DEFINED ARRAY EXAMPLES
      COMMON UNIDIMENSIONAL
   - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
  
$arr01a = array(2, 8, 18, 32, 32, 18, 8);
print_r($arr01a);
echo '<br><br>';

$arr01b = [ 2, 8, 18, 32, 32, 18, 8 ];
print_r($arr01b);
echo '<br><br>'; 

$arr01c = [ 2, 8, '18', 32, 'THIRTY-TWO', "eighteen", 8 ];
print_r($arr01c);
echo '<br><br>';

$arr01d = [ 299792458, 6.67428E-11, 'c', "G" ];
print_r($arr01d);
echo '<br><br>';

$arr01e = [01023, 0B0011, 0x20b ];
print_r($arr01e);
echo '<br><br>';

?>

 RESULT   

$arr01a =
Array ( [0] => 2 [1] => 8 [2] => 18 [3] => 32 [4] => 32 [5] => 18 [6] => 8 )

$arr01b =
Array ( [0] => 2 [1] => 8 [2] => 18 [3] => 32 [4] => 32 [5] => 18 [6] => 8 )

$arr01c =
Array ( [0] => 2 [1] => 8 [2] => 18 [3] => 32 [4] => THIRTY-TWO [5] => eighteen [6] => 8 )

$arr01d =
Array ( [0] => 299792458 [1] => 6.67428E-11 [2] => c [3] => G )

$arr01e =
Array ( [0] => 531 [1] => 3 [2] => 523 )

  2 EXERCISE   

<?php

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
        SOME USER-DEFINED ARRAY EXAMPLES
        UNIDIMENSIONAL ASSOCIATIVE
   - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

$arr02a = array('K' => 2, "L" => 8, "M" => 18,
"N" => 32, "O" => 32, "P" => 18, "Q" => 8);

print_r($arr02a);
echo '<br><br>';

$arr02b = [ 'K' => 2, "L" => 8, "M" => 18,
"N" => 32, "O" => 32, "P" => 18, "Q" => 8 ];

print_r($arr02b);
echo '<br><br>';

$arr02c = [ 'THIRTY-TWO' => 32, "EIGHTEEN" => 18 ];

print_r($arr02c);
echo '<br><br>';

$arr02d = [ 'c' => 299792458, 'G' => 6.67428E-11 ];
print_r($arr02d);
echo '<br><br>';

$arr02e = [ 2 => 'two', 4 => 'four' ];
print_r($arr02e);
echo '<br><br>';

?>

 RESULT   

$arr02a =
Array ( [K] => 2 [L] => 8 [M] => 18 [N] => 32 [O] => 32 [P] => 18 [Q] => 8 )

$arr02b =
Array ( [K] => 2 [L] => 8 [M] => 18 [N] => 32 [O] => 32 [P] => 18 [Q] => 8 )

$arr02c =
Array ( [THIRTY-TWO] => 32 [EIGHTEEN] => 18 )

$arr02d =
Array ( [c] => 299792458 [G] => 6.67428E-11 )

$arr02e =
Array ( [2] => two [4] => four )

  3 EXERCISE   

<?php

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
       SOME USER-DEFINED ARRAY EXAMPLES
       COMMON MULTIDIMENSIONAL
   - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */ 

$arr03a = array(2, 8, 18, 32, array (32, 18, 8));

print_r($arr03a);
echo '<br><br>';

$arr03b = [ 2, 8, 18, 32, [ 32, 18, 8 ] ];

print_r($arr03b);
echo '<br><br>';

$arr03c = [ 2, 8, '18', 32, [ 'THIRTY-TWO', "eighteen", 8 ] ];

print_r($arr03c);
echo '<br><br>';

$arr03d = [ 299792458, 6.67428E-11, [ 'c', "G" ] ];

print_r($arr03d);
echo '<br><br>';

$arr03e = [ ['01023', '0B0011', '0x20b'],
['octal', 'binary', 'hexadecimal' ] ];

print_r($arr03e);
echo '<br><br>';

$arr03f = ["Countries", "Continents",
["Brasil", "Portugal", "Japan"],
["South America", "Europe", "Asia"] ];

print_r($arr03f);
echo '<br><br>';

?>

 RESULT   

$arr03a =
Array ( [0] => 2 [1] => 8 [2] => 18 [3] => 32 [4] => Array ( [0] => 32 [1] => 18 [2] => 8 ) )

$arr03b =
Array ( [0] => 2 [1] => 8 [2] => 18 [3] => 32 [4] => Array ( [0] => 32 [1] => 18 [2] => 8 ) )

$arr03c =
Array ( [0] => 2 [1] => 8 [2] => 18 [3] => 32 [4] => Array ( [0] => THIRTY-TWO [1] => eighteen [2] => 8 ) )

$arr03d =
Array ( [0] => 299792458 [1] => 6.67428E-11 [2] => Array ( [0] => c [1] => G ) )

$arr03e =
Array ( [0] => Array ( [0] => 01023 [1] => 0B0011 [2] => 0x20b ) [1] => Array ( [0] => octal [1] => binary [2] => hexadecimal ) )

$arr03f =
Array ( [0] => Countries [1] => Continents [2] => Array ( [0] => Brasil [1] => Portugal [2] => Japan ) [3] => Array ( [0] => South America [1] => Europe [2] => Asia ) )

  4 EXERCISE   

<?php

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
         SOME USER-DEFINED ARRAY EXAMPLES
         ASSOCIATIVE MULTIDIMENSIONAL
   - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

$arr04a = array ("Countries" => array("Brasil", 
                                                           "Portugal", 
                                                           "Japan"),
"Continents" => array ("South America", 
                                   "Europe", 
                                   "Asia"));

$arr04b = [ "Countries" => [ "Brasil", 
                                           "Portugal", 
                                           "Japan" ],
"Continents" =>  ["South America", 
                          "Europe", 
                          "Asia"]];

print_r($arr04a);

echo '<br><br>';

print_r($arr04b);


$arr04c = [ "Countries" => [ 'BRA' => "Brasil", 
                                         'POR' => "Portugal", 
                                         'JPN' => "Japan" ],
           "Continents" =>  ['SA' => "South America", 
                                     'EU' => "Europe", 
                                     'AS' => "Asia"] ];
                                     
echo '<br><br>';

print_r($arr04c);

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

   PAY ATTENTION ON THE NEXT TWO EXAMPLES
   print_r is set with bool $return = TRUE, (true)
   
   No data is printed because $return was set 
   to TRUE or true - however, all information 
   on ARRAY elements is returned without problems
   
  - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

$arr04d = [ "Countries" => [ "Brasil", 
                                           "Portugal", 
                                           "Japan" ],  
           "Continents" =>  ["South America", 
                                     "Europe", 
                                     "Asia"] ];

echo '<br><br>';                                     
  
print_r($arr04d, TRUE);   

 
$arr04e = [ "Countries" => ['BRA' => "Brasil", 
                                       'POR' => "Portugal", 
                                       'JPN' => "Japan" ],   
           "Continents" =>  ['SA' => "South America", 
                                    'EU' => "Europe", 
                                    'AS' => "Asia"] ];

echo '<br><br>';                                    
   
print_r($arr04e, true);   

?>

 RESULT   

$arr04a =
Array ( [Countries] => Array ( [0] => Brasil [1] => Portugal [2] => Japan ) [Continents] => Array ( [0] => South America [1] => Europe [2] => Asia ) )

$arr04b =
Array ( [Countries] => Array ( [0] => Brasil [1] => Portugal [2] => Japan ) [Continents] => Array ( [0] => South America [1] => Europe [2] => Asia ) )

$arr04c =
Array ( [Countries] => Array ( [BRA] => Brasil [POR] => Portugal [JPN] => Japan ) [Continents] => Array ( [SA] => South America [EU] => Europe [AS] => Asia ) )


No data is printed because $return was set to TRUE or true - however, all information on ARRAY elements is returned without problems:

$arr04d =

$arr04e =

See the next exercise.

  5 EXERCISE   

<?php

$arr05a = [ "Countries" => [ "Brasil", 
                                          "Portugal", 
                                          "Japan" ], 
              "Continents" =>  ["South America", 
                                         "Europe", 
                                         "Asia"]];
 
print_r($arr05a, TRUE);  
echo '<br><br>';

$arr05b = 
  [ "Countries" => [ 'BRA' => "Brasil", 
                            'POR' => "Portugal", 
                            'JPN' => "Japan" ],  
    "Continents" =>  ['SA' => "South America", 
                              'EU' => "Europe", 
                              'AS' => "Asia"] ];

print_r($arr05a, true);  
echo '<br><br>';

print_r($arr05b['Countries']);
echo '<br><br>';
print_r($arr05b['Continents']);

?>

 RESULT   

In either case, no data will be printed.
Only the information returned is distributed without being displayed.

print_r is set with $return = TRUE (true).

In this example we have the ARRAYS elements available:

Array ( [BRA] => Brasil [POR] => Portugal [JPN] => Japan )
and
Array ( [SA] => South America [EU] => Europe [AS] => Asia )

  6 EXERCISE   

<?php 

$str06a = 'Lorem ipsum inceptos mollis eros risus ut luctus
 taciti, morbi viverra lorem et phasellus in vitae ultrices,
 neque torquent at condimentum felis vel nullam.';

$nbr06a = 1.23454;

print_r($str06a);

echo '<br><br>';

print_r($nbr06a);

?> 

 RESULT   

Lorem ipsum inceptos mollis eros risus ut luctus taciti, morbi viverra lorem et phasellus in vitae ultrices, neque torquent at condimentum felis vel nullam.

1.23454


  7 EXERCISE   

<?php 

$v07a = 5.455_052e-10;
// float
$v07b = 300_482_381;
// decimal
$v07c = 0xBBFF_3E48;
// hexadecimal
$v07d = 0b0101_1111;
// binary

// Representations available since the PHP 7.4.0

print_r ('$v07a = ' . $v07a);

print_r ('<br><br>$v07b = ' . $v07b);

print_r ('<br><br>$v07c = ' . $v07c);

print_r ('<br><br>$v07d = ' . $v07d);

?> 

 RESULT   

$v07a = 5.455052E-10

$v07b = 300482381

$v07c = 3154067016

$v07d = 95

It does not matter what the base of the VARIABLE was originally defined, as the result will always be expressed in base 10.