PHP script to get all keys from an array that starts with a certain string

In PHP, you can filter array keys that start with a specific string using several approaches. Each method offers different advantages depending on your coding style and requirements.

Method 1: Using foreach with explode()

This method uses explode() to split keys by a delimiter and check the first part ?

<?php
$arr_main_array = array('test_val' => 123, 'other-value' => 456, 'test_result' => 789);
$arr_result = array();

foreach($arr_main_array as $key => $value){
    $exp_key = explode('_', $key);
    if($exp_key[0] == 'test'){
        $arr_result[$key] = $value;
    }
}

if(!empty($arr_result)){
    print_r($arr_result);
}
?>

Array
(
    [test_val] => 123
    [test_result] => 789
)

Method 2: Using array_filter() with strpos()

A functional approach using array_filter() with ARRAY_FILTER_USE_KEY flag ?

<?php
$array = array('foo-bar' => 1, 'foo-baz' => 2, 'other' => 3, 'foo-test' => 4);

$filtered = array_filter($array, function($key) {
    return strpos($key, 'foo-') === 0;
}, ARRAY_FILTER_USE_KEY);

print_r($filtered);
?>

Array
(
    [foo-bar] => 1
    [foo-baz] => 2
    [foo-test] => 4
)

Method 3: Using foreach with strpos()

A procedural approach using strpos() to check if the key starts with the target string ?

<?php
$array = array('test_name' => 'John', 'test_age' => 25, 'user_id' => 100);
$result = array();

foreach ($array as $key => $value) {
    if (strpos($key, 'test_') === 0) {
        $result[$key] = $value;
    }
}

print_r($result);
?>

Array
(
    [test_name] => John
    [test_age] => 25
)

Method 4: Using ArrayIterator

An object-oriented approach using ArrayIterator for traversing the array ?

<?php
$array = array('foo-item1' => 'value1', 'bar-item2' => 'value2', 'foo-item3' => 'value3');
$i = new ArrayIterator($array);
$result = array();

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

print_r($result);
?>

Array
(
    [foo-item1] => value1
    [foo-item3] => value3
)

Comparison

Conclusion

Use array_filter() with strpos() for the most efficient and clean solution. Choose foreach approaches when you need additional custom logic during the filtering process.