PHP Array Functions

How to change array key case to upper or lower?

To change array keys to upper or lower case following function is used:

<?php

// declare cars array
$carsList = [
    'mazda'  => 'GS/GT',
    'toyota' => 'Corolla'
];

// change array keys to uppercase
$carsList = array_change_key_case($carsList, CASE_UPPER);

// show results
print_r($carsList);

// change array keys to lowercase
$carsList = array_change_key_case($carsList);

// show results
print_r($carsList);​

How to fetch specific keys as array from multi-dimensional array?

If you have a multi-dimensional array and you want to retrieve particular keys as an array you can easily do this using following array function.

<?php

// assume database returns
// arrays of records as below
$records = array(
    array(
        'id' => 2135,
        'first_name' => 'John',
        'last_name' => 'Doe',
    ),
    array(
        'id' => 3245,
        'first_name' => 'Sally',
        'last_name' => 'Smith',
    ),
    array(
        'id' => 5342,
        'first_name' => 'Jane',
        'last_name' => 'Jones',
    ),
    array(
        'id' => 5623,
        'first_name' => 'Peter',
        'last_name' => 'Doe',
    )
);

// get all the first names
$first_names = array_column($records, 'first_name');

// get all the last names but keep id as array keys
$last_names = array_column($records, 'last_name', 'id');

// debug array
var_dump($first_names, $last_names);​

How to merge arrays in php?

To mege array in php array_merge function is used. Followings are some of the hight lights of this function

• It merges two arrays into one
• If both array has common keys values from the second array will be considered
• New array elements will be appeneded.
• Numeric keys will be renumbered.

<?php

// prepare keys and value array
$valArray = ['color' => 'red', 'vehicle' => 'car', 'circle'];
$keyArray = ['color' => 'blue', 'vehicle' => 'truck', 'shape' => 'rectangle'];

// combine keys and values
$combinedArr = array_merge($keyArray, $valArray);
print_r($combinedArr);


// If you want to append array elements from the second array to the first array
// while not overwriting the elements from the first array and not re-indexing
// The keys from the first array will be preserved
// If an array key exists in both arrays, then the element from the first array will be used
$array1 = ['one', 'two', 'three'];
$array2 = ['four', 'five', 'six', 'seven'];

$result = $array1 + $array2;
print_r($result);


// observe the difference
// prepare keys and value array
$keyArray = ['color', 'vehicle', 'shape'];
$valArray = ['blue', 'truck', 'rectangle'];

$combined = array_combine($keyArray, $valArray);
print_r($combined);​

How to get list of array keys and values?

Followings are some of the useful function that deals with array keys and values:

<?php

// declare colors array
$colors  = ['blue', 'red', 'blue', 'green', 'yellow', 'blue'];

// get all keys for colors array
$keys = array_keys($colors);
$blueKeys = array_keys($colors, "blue");

// get all values for colors array
$values = array_values($colors);

// debug
print_r($keys);
print_r($values);
print_r($blueKeys);

// get first key of colors array
$firstKey = array_key_first($colors);

// get last key of colors array
$lastKey = array_key_last($colors);​

How to count repeated values in array?

<?php

// declare colors array
$colors  = ['blue', 'red', 'blue', 'green', 'yellow', 'blue'];

// find number of times value appeared in an array
$result = array_count_values($colors);

// count total elements in array
$total = count($colors);

// debug
print_r($total);
print_r($result);​

How to sort arrays in php?

Followings are some of the functions that can help you with array sorting:

<?php

// How to sort array values?
$colors  = ['blue', 'red', 'blue', 'aqua', 'green', 'yellow', 'blue'];

// duplicate array
$colors2 = $colors;
$colors3 = $colors;
$colors4 = $colors;

// sort an array by value
// does not maintain indexes/keys
sort($colors);
print_r($colors);

// sort an array by value
// maintain indexes/keys
asort($colors2);
print_r($colors2);


// sort an array in reverse
// order from high to low
rsort($colors);
print_r($colors);

// sort an array by values using
// a user-defined comparison function
// does not maintain indexes/keys
usort($colors3, function ($a, $b) {
    return $a <=> $b;
});

print_r($colors3);

// sort an array by values using
// a user-defined comparison function
// maintain indexes/keys
uasort($colors4, function ($a, $b) {
    return $a <=> $b;
});

print_r($colors4);


// define multi-dimensional array
$multiArr = [
  ['a' => 1, 'b' => 2, 'c' => 2],
  ['a' => 4, 'b' => 5, 'c' => 4],
  ['a' => 7, 'b' => 8, 'c' => 3],
];

$keyToSort = 'c';
usort($multiArr, function ($a, $b) use ($keyToSort) {
    return $a[$keyToSort] <=> $b[$keyToSort];
});

print_r($multiArr);


// How to sort array keys?
$colors  = ['blue' => 1, 'red' => 2, 'aqua' => 4, 'green' => 5, 'yellow' => 6];

// sort an array by keys using
// a user-defined comparison function
uksort($colors, function ($a, $b) {
    return $a <=> $b;
});

print_r($colors);​

Sorting functions in php