Learn a new php function every day (2) array_diff()/array_diff_key()/array_diff_assoc()

array_diff( array array1, array array2 [, array …] )

Description
array_diff() returns an array containing all values ​​in array1 that are not in any other argument array. Note that the key names remain unchanged.

Liezi

<code><!--?php
    $array1 = array("a" =--> "green", "red", "blue", "red");
    $array2 = array("b" => "green", "yellow", "red");
    $result = array_diff($array1, $array2);
    print_r($result);
?>
</code>

The output result is

<code>Array([1] => blue)
</code>

Attention

Two cells are considered identical only if (string) $elem1 === (string) $elem2. That is, when the string expressions are the same. Note that this function only checks one dimension of a multidimensional array. Of course you can use array_diff($array1[0], $array2[0]); to check deeper dimensions.

array array_diff_assoc ( array array1, array array2 [, array …] )

Description
array_diff_assoc() returns an array containing all values ​​in array1 that are not in any other argument array. Note that unlike array_diff(), key names are also used for comparison.
Lie Zi

<code><!--?php
    $array1 = array("a" =--> "green", "b" => "brown", "c" => "blue", "red");
    $array2 = array("a" => "green", "yellow", "red");
    $result = array_diff_assoc($array1, $array2);
    print_r($result);
?> 
</code>

Output

<code>Array(
    [b] => brown
    [c] => blue
    [0] => red
)
</code>

In the above example, you can see that the key-value pair "a" => "green" is present in both arrays, so it is not included in the output of this function. In contrast, the key-value pair 0 => "red" appears in the output because the key of "red" in the second parameter is 1.

Liezi 2

<code><!--?php
    $array1 = array(0, 1, 2);
    $array2 = array("00", "01", "2");
    $result = array_diff_assoc($array1, $array2);
    print_r($result);
?--> 
</code>

Output

<code>Array(
    [0] => 0
    [1] => 1
）    
</code>

Two values ​​in the key => value pair are considered equal only if (string) elem1===(string)elem2. That is to say, strict checking is used, and the expressions of the strings must be the same.

Attention

Note: Note that this function only checks one dimension of the multi-dimensional array. Of course you can use array_diff_assoc($array1[0], $array2[0]); to check deeper dimensions.

array array_diff_key ( array $array1 , array $array2 [, array $… ] )

Description
Compare the key names in array1 with array2 and return items with different key names. This function is the same as array_diff() except that the comparison is based on keys rather than values.
Returns an array containing the values ​​of all keys that appear in array1 but do not appear in any other parameter array.

Liezi

<code><!--?php
    $array1 = array('blue'  =--> 1, &#39;red&#39;  => 2, &#39;green&#39;  => 3, &#39;purple&#39; => 4);
    $array2 = array(&#39;green&#39; => 5, &#39;blue&#39; => 6, &#39;yellow&#39; => 7, &#39;cyan&#39;   => 8);

    var_dump(array_diff_key($array1, $array2));
?> 
</code>

Output

<code>array(2) {
  ["red"]=>
  int(2)
  ["purple"]=>
  int(4)
}
</code>

Two key names in a key => value pair are considered equal only if (string)$key1 === (string) $key2 . In other words, strict type checking is performed, so the string representations must be exactly the same.

array array_intersect ( array $array1 , array $array2 [, array $ … ] )

Description
array_intersect() returns an array containing all values ​​in array1 that are also present in all other argument arrays. Note that the key names remain unchanged.