<?php
$a = array("1");
var_dump(array_fill_keys($a, "test"));
?>
array(1) {
  [1]=>
  string(4) "test"
}
now string key "1" become an integer value 1, be careful.(PHP 5 >= 5.2.0, PHP 7, PHP 8)
array_fill_keys — 使用指定的键和值填充数组
keys使用该数组的值作为键。非法值将被转换为字符串。
value填充使用的值。
返回填充后的数组。
示例 #1 array_fill_keys() 示例
<?php
$keys = array('foo', 5, 10, 'bar');
$a = array_fill_keys($keys, 'banana');
print_r($a);
?>以上示例会输出:
Array
(
    [foo] => banana
    [5] => banana
    [10] => banana
    [bar] => banana
)
<?php
$a = array("1");
var_dump(array_fill_keys($a, "test"));
?>
array(1) {
  [1]=>
  string(4) "test"
}
now string key "1" become an integer value 1, be careful.If an associative array is used as the second parameter of array_fill_keys, then the associative array will be appended in all the values of the first array.
e.g.
<?php
$array1 = array(
    "a" => "first",
    "b" => "second",
    "c" => "something",
    "red"
);
$array2 = array(
    "a" => "first",
    "b" => "something",
    "letsc"
);
print_r(array_fill_keys($array1, $array2));
?>
The output will be
Array(
    [first] => Array(
        [a] => first,
        [b] => something,
        [0] => letsc
    ),
    [second] => Array(
        [a] => first,
        [b] => something,
        [0] => letsc
    ),
    [something] => Array(
        [a] => first,
        [b] => something,
        [0] => letsc
    ),
    [red] => Array(
        [a] => first,
        [b] => something,
        [0] => letsc
    )
)Get an associative array of zeros for counting letter frequency
<?php
$ltrs = array_fill_keys( range('a', 'z'), 0 );RE: bananasims at hotmail dot com
I also needed a work around to not having a new version of PHP and wanting my own keys. bananasims code doesn't like having an array as the second parameter...
Here's a slightly modified version than can handle 2 arrays as inputs:
//we want these values to be keys
$arr1 = (0 => "abc", 1 => "def");
/we want these values to be values
$arr2 = (0 => 452, 1 => 128);
function array_fill_keys($keyArray, $valueArray) {
    if(is_array($keyArray)) {
        foreach($keyArray as $key => $value) {
            $filledArray[$value] = $valueArray[$key];
        }
    }
    return $filledArray;
}
array_fill_keys($arr1, $arr2);
returns:
abc => 452, def =>128Some of the versions do not have this function.
I try to write it myself.
You may refer to my script below
function array_fill_keys($array, $values) {
    if(is_array($array)) {
        foreach($array as $key => $value) {
            $arraydisplay[$array[$key]] = $values;
        }
    }
    return $arraydisplay;
}see array_fill_keys are basically used to make a new array from a pre-existing array in a form that the value of the pre-existing array will now be the key of the new Array .And there value will be same That we had given in the 2nd parameter . Example Below---->>>
<?php
        //pre existing array
        $a = array("a","b","c","d","e");
        //new array with a single same value 
        $newArray = array_fill_keys($a, "Testing");
        //printing the array 
        echo "<pre>";
        print_r($newArray);
        echo "</pre>";
?>
output;
    Array
(
    [a] => Testing
    [b] => Testing
    [c] => Testing
    [d] => Testing
    [e] => Testing
)