PHP array_keys

 PHP array_keys is used to find the key value in the PHP array. It can simply output all the key values, or you can add conditions to let array_keys help you find the specific key value. This array function can only judge the key value of the PHP Array . It is not used to find array elements.

PHP array_keys syntax example

array array_keys (fill in the array to be queried, fill in the specific array element you are looking for);

In the example, the "fill in the array to be queried" is a required item, and it must be a PHP Array . As for "fill in the specific array element you are looking for", it is an optional item to tell PHP array_keys you want To find the specific key value, please refer to the following example.

PHP array_keys implementation example

<?php
$Arr = array("0" => "A", "1" => "B" );
print_r(array_keys($Arr));　// 會輸出 Array ( [0] => 0 [1] => 1 )

$Arr = array("0" => "A", "1" => "B" , "2" => "C" , "3" => "B" );
print_r(array_keys($Arr,B));　// 會輸出 Array ( [0] => 1 [1] => 3 )
?>

The first group of examples does not add any specific conditions, so array_keys directly stores all the key values ​​into an array and then outputs it. This part is relatively no problem. Note that the second group of examples has already added the key with the key value B before outputting. So the final printed result has only two key values.