PHP, Structures and Functions of ARRAY

This function returns an ARRAY containing all the entries from $array1 that are present in any of the other arrays.

Multiple occurrences in $array1 are all treated the same way.

In order for two elements to be considered identical, they must have the same keys.


<?php

arr array_intersect_key ( arr $array1 , arr $array2 [, 
                                       arr $arra3, ..., arr $arrayN ] )
 

where,

$array1 = The first ARRAY to keys check

$array2 = The second ARRAY to compare keys against

$array3 = The third ARRAY to compare keys against

. . . . . . . . . . . . . . .

$arrayN = The last ARRAY to compare keys against

?>

$array1

The first ARRAY - keys to check.

$array2

The second ARRAY - to compare keys against.

$array3

The third ARRAY - to compare keys against.

$arrayN

The last ARRAY - to compare keys against.

EXERCISE


 <?php

$az1 = [ "wa" => "Water", 
              "co" => "Cobalt",
              "cy" => "Cyan",
              "he" => "Heavenly", 
              "ca" => "Cadet" ];

$az2 = [ "ca" => "Cadet", 
              "ma" => "Marine", 
              "sl" => "Slate", 
              "pe" => "Petroleum",
              "cy" => "Cyan" ];

$az3 = [ "ma" => "Marine", 
              "ca" => "Cadet", 
              "re" => "Real", 
              "cy" => "Cyan", 
              "na" => "Naval" ];
              
echo 'FIRST ARRAY:<br>';

print_r($az1);

echo '<br><br>SECOND ARRAY:<br>';

print_r($az2);

echo '<br><br>THIRD ARRAY:<br>';

print_r($az3);

echo '<br><br><br>RESULTING ARRAY:<br>';

$az123 = array_intersect_key($az1, $az2, $az3);

print_r($az123);

?>

RESULT

FIRST ARRAY:
Array ( [wa] => Water [co] => Cobalt [cy] => Cyan [he] => Heavenly [ca] => Cadet )

SECOND ARRAY:
Array ( [ca] => Cadet [ma] => Marine [sl] => Slate [pe] => Petroleum [cy] => Cyan )

THIRD ARRAY:
Array ( [ma] => Marine [ca] => Cadet [re] => Real [cy] => Cyan [na] => Naval )

RESULTING ARRAY:
Array ( [cy] => Cyan [ca] => Cadet )

All keys are the same in all ARRAYS worked by this function.

All values also belong to the first ARRAY.

EXERCISE


 <?php

$tean1 = [ "CORINTHIANS", "PALMEIRAS", 
                         "SANTOS", "SÃO PAULO", "GRÊMIO" ];

$tean2 = [ "VASCO", "CRUZEIRO", "FLUMININSE", "SANTOS" ];

$tean3 = [ "VASCO", "GRÊMIO", "VITÓRIA", "SANTOS", "BAHIA" ];
              
echo 'FIRST ARRAY:<br>';

print_r($tean1);

echo '<br><br>SECOND ARRAY:<br>';

print_r($tean2);

echo '<br><br>THIRD ARRAY:<br>';

print_r($tean3);

echo '<br><br><br>RESULTING ARRAY:<br>';

$tean123 = array_intersect_key($tean1, $tean2, $tean3);

print_r($tean123);

?>

RESULT

FIRST ARRAY:
Array ( [0] => CORINTHIANS [1] => PALMEIRAS [2] => SANTOS [3] => SÃO PAULO [4] => GRÊMIO )

SECOND ARRAY:
Array ( [0] => VASCO [1] => CRUZEIRO [2] => FLUMININSE [3] => SANTOS )

THIRD ARRAY:
Array ( [0] => VASCO [1] => GRÊMIO [2] => VITÓRIA [3] => SANTOS [4] => BAHIA )

RESULTING ARRAY:
Array ( [0] => CORINTHIANS [1] => PALMEIRAS [2] => SANTOS [3] => SÃO PAULO )

All keys are the same in all ARRAYS worked by this function.

All values also belong to the first ARRAY.

EXERCISE


 <?php

$color1 = [ "Yellow", "Green", "Red", "Blue", "Rose" ];

$color2 = [ 'cy' => "Cyan", 'ma' => "Magenta", "Blue" ];

$color3 = [ 'cy' => "Cyan", 'ro' => "Rose", "Blue" ];
              
echo 'FIRST ARRAY:<br>';

print_r($color1);

echo '<br><br>SECOND ARRAY:<br>';

print_r($color2);

echo '<br><br>THIRD ARRAY:<br>';

print_r($color3);

echo '<br><br><br>RESULTING ARRAY:<br>';

$color123 = array_intersect_key($color1, $color2, $color3);

print_r($color123);

?>

RESULT

FIRST ARRAY:
Array ( [0] => Yellow [1] => Green [2] => Red [3] => Blue [4] => Rose )

SECOND ARRAY:
Array ( [cy] => Cyan [ma] => Magenta [0] => Blue )

THIRD ARRAY:
Array ( [cy] => Cyan [ro] => Rose [0] => Blue )

RESULTING ARRAY:
Array ( [0] => Yellow )

The unique value that displays the same index key in the first ARRAY is 'Yellow' whose key is ZERO.

EXERCISE


<?php

/*
* Function is implemented in ext/standard/array.c
*/

$array1 = array('blue' => 1, 'red' => 2,
                                       'green' => 3, 'purple' => 4);
$array2 = array('green' => 5, 'blue' => 6, 
                                           'yellow' => 7, 'cyan' => 8);

echo 'The given $array1:<br>';
var_dump($array1);

echo '<br><br>The given $array2:<br>';
var_dump($array2);

echo '<br><br><br>
            After array_intersect_key($array1, $array2):<br>';
var_dump(array_intersect_key($array1, $array2));

?>

EXERCISE


<?php

echo "Testing array_intersect_key() : usage variation.";

// Initialise function arguments 
// not being substituted (if any)
$input_array = [ 0 => '0', -1 => '-1' , 02 => 'two', 
                                    -07 => '-07', 0xA => '0xA', 
                                  -0xC => '-0xc' ];

$input_arrays = [
      'decimal indexed' => [ 10 => '10', '-17' => '-17' ],
       'octal indexed' => [ -011 => '-011', 012 => '012' ],
       'hexa  indexed' => [0x12 => '0x12', -0x7 => '-0x7', ],
];

echo '<br><br>The given $input_array:<br>';
var_dump($input_array);

echo '<br><br>The given $input_arrays:<br>';
var_dump($input_arrays);

foreach($input_arrays as $key =>$value) {
      echo "<br><br><b>$key:</b>";

echo '<br>
         After array_intersect_key($input_array, $value):<br>';      
      var_dump( array_intersect_key($input_array, $value) );
echo '<br><br>
     After array_intersect_key($value,$input_array):<br>';          
      var_dump( array_intersect_key($value,$input_array) );
}

?>

EXERCISE


<?php

echo "Testing array_intersect_key() : usage variation.";

// Initialise function arguments not being substituted (if any)
$input_array = array(0 => '0', 
                                10 => '10', 
                              -10 => '-10');
$float_indx_array = array(0.0 => '0.0', 
                                        10.5 => '10.5', 
                                       -10.5 => '-10.5', 
                                         0.5 => '0.5');

echo '<br><br>The given $input_array:<br>';
var_dump($input_array);

echo '<br><br>The given $float_indx_array:<br>';
var_dump($float_indx_array);

echo "<br><br>With float indexed array.<br>";
echo 'After 
 array_intersect_key($input_array, $float_indx_array):<br>';  
var_dump( array_intersect_key($input_array, 
                                                 $float_indx_array) );

echo '<br><br>After 
  array_intersect_key($float_indx_array, $input_array):<br>';
var_dump( array_intersect_key($float_indx_array,
                                                 $input_array));

?>

EXERCISE


<?php

echo "Testing array_intersect_key() : usage variation.";

// Initialise function arguments not being substituted (if any)
$input_array = array(0 => '0', 
                                 1 => '1' , 
                              -10 => '-10');
$boolean_indx_array = array(true => 'boolt', false => 'boolf', 
                                             TRUE => 'boolT', FALSE => 'boolF');

echo '<br><br>The given $input_array:<br>';
var_dump($input_array);

echo '<br><br>The given $boolean_indx_array<br>';
var_dump($boolean_indx_array);

echo "<br><br>With boolean indexed array.<br>";
echo 'After 
 array_intersect_key($input_array, $boolean_indx_array):<br>';  
var_dump( array_intersect_key($input_array, 
                                                 $boolean_indx_array) );

echo '<br><br>After 
  array_intersect_key($boolean_indx_array, $input_array):<br>';
var_dump( array_intersect_key($boolean_indx_array, 
                                                 $input_array) );

?>

EXERCISE


<?php

echo "Testing array_intersect_key() : usage variation.";

// Initialise function arguments not being substituted (if any)
$input_array = array(0 => '0', 1 => '1' , -10 => '-10' , null => 'null');
//get an unset variable
$unset_var = 10;
unset ($unset_var);

$input_arrays = array(
'null indexed' => array(NULL => 'null 1', null => 'null 2'),
'undefined indexed' => array(@$undefined_var => 'undefined'),
'unset  indexed' => array(@$unset_var => 'unset'),
);

echo '<br><br>The given $input_array:<br>';
var_dump($input_array);

echo '<br><br>The given $input_arrays:<br>';
var_dump($input_arrays);

foreach($input_arrays as $key =>$value) {
      echo "<br><br><b>$key:</b><br>";

echo 'After array_intersect_key($input_array, $value):<br>';      
      var_dump( array_intersect_key($input_array, $value) );
echo '<br><br>
     After array_intersect_key($value,$input_array):<br>';          
      var_dump( array_intersect_key($value,$input_array) );
}

?>

EXERCISE


<?php

echo "Testing array_intersect_key() : usage variation.";

/// Initialise function arguments not being substituted (if any)
$array1 = array(

      'first' => array('blue'  => 1, 'red'  => 2),

      'second' => array('yellow' => 7),

      'third' => array(0 =>'zero'),
);

$array2 = array (

      'first' => array('blue'  => 1, 'red'  => 2,),

      'second' => array('cyan'   => 8),

      'fourth' => array(2 => 'two'),
);

echo '<br><br>The given $array1:<br>';
var_dump($array1);

echo '<br><br>The given $array2:<br>';
var_dump($array2);

echo '<br><br><br>After array_intersect_key($array1, $array2):<br>';
var_dump( array_intersect_key($array1, $array2) );

echo '<br><br><br>After array_intersect_key($array2, $array1):<br>';
var_dump( array_intersect_key($array2, $array1 ) );

?>