Get all keys from an array that starts with a certain string

Hello Devs!

In this post, I will show you how to get all keys from an array that starts with a certain string. I will show you a simple example of PHP array filtering only certain keys. I will help you to give some examples of getting all key-value starting with a certain string from a PHP array. It's gonna be a simple example of PHP array_filter_key() function. So, Let's see below examples of PHP array gets all keys to start with a specific string.

I will provide 4 examples here.

So, let's start one by one.

Example 1:

<?php
  
    $arr = [
        'fb-1' => 'One',
        'fb-2' => 'Two',
        '3' => 'Three',
        'fb-4' => 'Four',
    ];
  
    $result = [];
    $startWith = 'fb';
    foreach($arr as $key => $value){
        $exp_key = explode('-', $key);
        if($exp_key[0] == $startWith){
            $result[] = $value;
        }
    }
  
    print_r($result);
  
?>

Output:Array
(
    [0] => One
    [1] => Two
    [2] => Four
)

Example 2:

It's gonna be a functional approach an array_filter_key() the function is taken and applied to an array of elements.

<?php
  
    $arr = [
        'fb-1' => 'One',
        'fb-2' => 'Two',
        '3' => 'Three',
        'fb-4' => 'Four',
    ];
  
    $result = array_filter_key($arr, function($key) {
       return strpos($key, 'fb-') === 0;
    });
  
    print_r($result);
  
?>

Output:

Array
(
    [0] => One
    [1] => Two
    [2] => Four
)

Example 3:

In the third example, we will use a procedural approach.

<?php
  
    $arr = [
        'fb-1' => 'One',
        'fb-2' => 'Two',
        '3' => 'Three',
        'fb-4' => 'Four',
    ];
  
    $result = [];
    foreach ($arr as $key => $value) {
        if (strpos($key, 'fb-') === 0) {
             $result[$key] = $value;
        }
    }
  
    print_r($result);

?>

Read also: How to get all dates between two dates in php

Output:

Array
(
    [0] => One
    [1] => Two
    [2] => Four
)

Example 4:

In the last example, we will use a procedural approach but use objects.

<?php
  
    $arr = [
        'fb-1' => 'One',
        'fb-2' => 'Two',
        '3' => 'Three',
        'fb-4' => 'Four',
    ];
  
    $result = [];
    $i = new ArrayIterator($arr);

    while ($i->valid()) {
         if (strpos($i->key(), 'fb-') === 0) {
              $result[$i->key()] = $i->current();
         }
         $i->next();
    }
  
    print_r($result);

?>

Output:

Array
(
    [0] => One
    [1] => Two
    [2] => Four
)

I hope it can be helpful.

Happy Coding :)