How to print array index? [closed]

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I want to print the array index for some purpose. Can anybody tell me about this ?

---

Get the first index of an elemnt:

$array = array(0 => 'blue', 1 => 'red', 2 => 'green', 3 => 'red');
$key = array_search('green', $array); // $key = 2;
echo $key;

For all elemnts

foreach($array as $key => $value){
    echo "{$key} => {$value}\n";
}

will output

0 => blue
1 => red
2 => green
3 => red

All keys:

echo implode(', ',array_keys($array));

will output

 0, 1, 2, 3

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not sure what you mean with this question but you could try

echo "<pre>";
print_r ($arr);
echo "</pre>";

that way you'll see your entire array including all the indexes

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if you mean the keys of the array:

$array = array(0 => 100, "color" => "red");
print_r(array_keys($array));

//result
Array
(
    [0] => 0
    [1] => color
)

This will provide an array of the keys