Handle PHP associative and indexed array in a single loop

select_options.php

<?php

//--------------------
function brian($i) {
	foreach ($i as $value => $name) {
		$value = (is_string($value) ? $value : $name);
		echo '<option value="' . $value . '">' . $name . '</option>' . PHP_EOL;
	}
}

//--------------------
// Breaks if there is even a single element with an associative (string) key.
function gus($i) {
	if( count( array_filter( array_keys( $i ), 'is_string' ) ) ) {
		foreach( $i as $value => $name ) {
			echo '<option value="' . $value . '">' . $name . '</option>' . PHP_EOL;
		}
	} else {
		foreach( $i as $value ) {
			echo '<option value="' . $value . '">' . $value . '</option>' . PHP_EOL;
		}
	}
}

//--------------------
// At least this approach means you don't have to manage the output format in multiple places.
function gus2($i) {
	if( count( array_filter( array_keys( $i ), 'is_string' ) ) ) {
		foreach( $i as $value => $name ) {
			gus2_helper($value, $name);
		}
	} else {
		foreach( $i as $value ) {
			gus2_helper($value);
		}
	}
}

function gus2_helper($value, $name = null) {
	$name = (is_null($name) ? $value : $name);
	echo '<option value="' . $value . '">' . $name . '</option>' . PHP_EOL;
}


// main() -----------------------
$input = array(
  'value1',
  'key1' => 'value2',
);

echo "Brian:\n";
brian($input);

echo "\nGus:\n";
gus($input);

echo "\nGus 2:\n";
gus2($input);

Output:

Brian:
<option value="value1">value1</option>
<option value="key1">value2</option>

Gus:
<option value="0">value1</option>
<option value="key1">value2</option>

Gus 2:
<option value="0">value1</option>
<option value="key1">value2</option>