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A detailed explanation of the array_change_key_case() function in PHP
- PHP中文网Original
- 2017-10-27 08:58:211187browse
array_change_key_case() Converts all keys of the array to uppercase letters:
<?php
/*
array_change_key_case() 返回其键均为大写或小写的数组。
array array_change_key_case(array input[,int case])
参数描述：array是要转换键值的数组
case有两个选项:CASE_LOWER，默认选项，以小写字母返回数组的键
CASE_UPPER,以大写字母返回数组的键
*/
$input_array = array('a'=>'Java',
'B'=>'Php',
'c'=>'C++',
'D'=>'C#');
print_r(array_change_key_case($input_array, CASE_LOWER));
print_r(array_change_key_case($input_array, CASE_UPPER));
//如果在运行该函数时两个或多个键相同，则最后的元素会覆盖其他元素，例如：
$input_array = array('a'=>'Barcelona',
'B'=>'Madrid',
'c'=>'Manchester',
'b'=>'Milan');
print_r(array_change_key_case($input_array, CASE_LOWER));
?>Definition and usage
array_change_key_case() function converts all keys of the array to uppercase letters or lowercase letter.
Syntax
array_change_key_case(array,case);
Parameters
Description
array Required. Specifies the array to use.
case Optional. Possible values:
CASE_LOWER - Default value. Convert an array's keys to lowercase letters.
CASE_UPPER - Convert array keys to uppercase letters.
Technical Details
Return value:
Returns an array with keys with lowercase letters, or returns with uppercase letters An array of letters with keys, or FALSE if array is not an array.
PHP version:
4.2+
Convert all keys of the array to lowercase letters:
<?php
$age=array("Peter"=>"35","Ben"=>"37","Joe"=>"43");
print_r(array_change_key_case($age,CASE_LOWER));
?> If after running array_change_key_case() there are two or more keys with the same key (such as "b" and "B"), the last element will overwrite the other elements:
<?php
$pets=array("a"=>"Cat","B"=>"Dog","c"=>"Horse","b"=>"Bird");
print_r(array_change_key_case($pets,CASE_UPPER));
?>More examples :
$cc = [
'0'=>[
'Abc'=>'asdfasdf',
'BBAbc'=>'asdfasdf',
'AbDDc'=>'asdfasdf',
]
];
$tmp = array_change_key_case($cc);
dump($tmp);
return;The printout result is
array (size=1)
0 =>
array (size=3)
'Abc' => string 'asdfasdf' (length=8)
'BBAbc' => string 'asdfasdf' (length=8)
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