Question 255646 in PHP Question posted in
Official manual can be found here.

how to get before comes string from array in php

i want to get before come array string from array like :

i want this type

$array=array('ABC','BCD','DCB','KBC');

// now iwant get BCD using DCB

echo get_beforestring('DCB',$array);

// I want result BCD

I don’t have any solution for this, if you have any please let me tally. I am trying to solve it but am not able to do so. Because I am new to PHP coding, I don’t have an answer to this question, do you have an answer?

Tags:

2

Answers


  1. 0

    The following function will do what you’ve asked for and return false if the needle is not found in the array or has no preceding value:

    <?php

function getPreviousValue($array, $value) {
    $key = array_search($value, $array);
    return ($key === false || !isset($array[$key-1])) ? false : $array[$key-1];
}

$array=array('ABC','BCD','DCB','KBC');

var_dump(getPreviousValue($array, 'DCB'));

//returns string(3) "BCD"

    If you also want it to work on arrays with non numeric indexes you could do:

    <?php

function getPreviousValue($array, $value) {
    $array = array_values($array);
    $key = array_search($value, $array);
    return ($key === false || !isset($array[$key-1])) ? false : $array[$key-1];
}

$array=array('a'=>'ABC','b'=>'BCD','c'=>'DCB','d'=>'KBC');

var_dump(getPreviousValue($array, 'DCB'));

//also returns string(3) "BCD"
    Login or Signup to reply.
  2. 0

    Logic

    1. Increment array key & compare the corresponding value with search item (for example ‘DCB’)

    2. If both are matching, decrement array key & then return the corresponding value. STOP

    3. Else if both does not match, go back to step 1

    Implementation

    Check following function that implements above logic inside a do-while loop

    function get_beforestring(string $needle, array $haystack): ?string {
    $key = 0; $penultimate_key = count($haystack)-2;
    if($haystack[$key]!=$needle) {
        do {
            if($haystack[++$key]==$needle)
            return $haystack[--$key];
        } while ($key<=$penultimate_key);
    }
    return null;
}

$array=array('ABC', 'BCD', 'DCB', 'KBC');
echo get_beforestring('DCB', $array);
    Login or Signup to reply.
Please signup or login to give your own answer.

Back To Top
Search