PHP determines array equality. Introduction to array operators_PHP tutorial

How to determine if two arrays are equal? It’s actually very simple, just use == or ===

The php manual explains as follows,

Example Name Result
$a + $b union The union of $a and $b.
$a == $b equal TRUE if $a and $b have the same key/value pair.
$a === $b Congruent TRUE if $a and $b have the same key/value pairs and are of the same order and type.
$a != $b does not equal TRUE if $a does not equal $b.
$a <> $b does not equal TRUE if $a does not equal $b.
$a !== $b is not equal TRUE if $a is not equal to $b.
Can multi-dimensional arrays like array('k'=>array()) be equal using the above method? Of course you can.

If the array is numerically indexed, you need to pay attention, see the code

[php]
$a = array("apple", "banana");
$b = array(1 => "banana", "0" => "apple");

var_dump($a == $b); // bool(true)
var_dump($a === $b); // bool(false)
?>

$a = array("apple", "banana");
$b = array(1 => "banana", "0" => "apple");

var_dump($a == $b); // bool(true)
var_dump($a === $b); // bool(false)
?>
In addition to the array operator ==, there are other more convoluted methods to judge. For example, use array_diff($a, $b) to compare the difference sets of two arrays. If the difference sets are NULL, they are equal.

Then let’s talk about the + plus operator of arrays. The difference between + and array_merge is that when equal keys are encountered, when + is used, the left array will overwrite the value of the right array. On the contrary, with array_merge, the latter array will overwrite the previous one.

[php]
$a = array("a" => "apple", "b" => "banana");
$b = array("a" => "pear", "b" => "strawberry", "c" => "cherry");

$c = $a + $b; // Union of $a and $b
echo "Union of $a and $b: n";
var_dump($c);

$c = array_merge($a, $b); // Union of $b and $a
echo "array_merge of $b and $a: n";
var_dump($c);
?>

$a = array("a" => "apple", "b" => "banana");
$b = array("a" => "pear", "b" => "strawberry", "c" => "cherry");

$c = $a + $b; // Union of $a and $b
echo "Union of $a and $b: n";
var_dump($c);

$c = array_merge($a, $b); // Union of $b and $a
echo "array_merge of $b and $a: n";
var_dump($c);
?>Output after execution:

[php]
Union of $a and $b:
array(3) {
["a"]=>
string(5) "apple"
["b"]=>
string(6) "banana"
["c"]=>
string(6) "cherry"
}
array_merge of $b and $a:
array(3) {
["a"]=>
string(4) "pear"
["b"]=>
string(10) "strawberry"
["c"]=>
string(6) "cherry"
}

Union of $a and $b:
array(3) {
["a"]=>
string(5) "apple"
["b"]=>
string(6) "banana"
["c"]=>
string(6) "cherry"
}
array_merge of $b and $a:
array(3) {
["a"]=>
string(4) "pear"
["b"]=>
string(10) "strawberry"
["c"]=>
string(6) "cherry"
}

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