Difference between “as $key => $value” and “as $value” in PHP foreach

Question

I have a database call and I\'m trying to figure out what the $key => $value does in a foreach loop.

The reason I ask is because both these

Answer 1

Sample Array: Left ones are the keys, right one are my values

$array = array(
        'key-1' => 'value-1', 
        'key-2' => 'value-2',
        'key-3' => 'value-3',
        );

Example A: I want only the values of $array

foreach($array as $value) {    
    echo $value; // Through $value I get first access to 'value-1' then 'value-2' and to 'value-3'     
}

Example B: I want each value AND key of $array

foreach($array as $key => $value) {                 
    echo $value; // Through $value I get first access to 'value-1' then 'value-2' and to 'value-3'  

    echo $key; // Through $key I get access to 'key-1' then 'key-2' and finally 'key-3'    

    echo $array[$key]; // Accessing the value through $key = Same output as echo $value;
    $array[$key] = $value + 1; // Exmaple usage of $key: Change the value by increasing it by 1            
}