Retrieve indexes of value in array - php

Question

Is it possible to search an array for a given value and return all the indexes at which the value was found? So for this array:
["Red","Green","Red","Blue"]
I need
[0,2]
with regard to a search for "Red". Searching for "Yellow" in this case would return an empty array.

Answer 1

You can use like this:
$array = ["Red","Green","Red","Blue"];
$output = array_keys($array, "Red");
The $output will be [0,2]

Answer 2

I think this should work:
$input = ["Red","Green","Red","Blue"];
$x = "Red";
$keys = array_keys(array_filter($input, function ($v) use ($x) { return $v === $x;}));

Answer 3

You can iterate the array with foreach:
foreach($input_arr as $key => $value){
if($value == 'Red'){
needed_key_arr[] = $key;
}
}
Also, if you can have an array of values you what to search use:
$lookup_arr = ['Red', 'Green'];
foreach($input_arr as $key => $value){
if(in_array($value, $lookup_arr)){
needed_key_arr[] = $key;
}
}

Answer 4

$arr = ["Red","Green","Red","Blue"];
$valueToSearchFor = ["Red"];
$keys = array_keys(array_filter($arr, function ($val1) use ($valueToSearchFor) { // filter the first array
return array_filter($valueToSearchFor, function ($val) use ($val1) { // use the first array's value
return $val == $val1; // compare them and then return them
});
}));
var_dump($keys) // array(2) { [0]=> int(0) [1]=> int(2) }
First we filter the array then take the values from the first filter to another filter then we match the arrays and we return them. This works for multiple values too.
$arr = ["Red","Green","Red","Blue"];
$valueToSearchFor = ["Red", "Blue"];
$keys = array_keys(array_filter($arr, function ($val1) use ($valueToSearchFor) {
return array_filter($valueToSearchFor, function ($val) use ($val1) {
return $val == $val1;
});
}));
var_dump($keys) // array(3) { [0]=> int(0) [1]=> int(2) [2]=> int(3) }