Deleting an element from an array in PHP

There are different ways to delete an array element, where some are more useful for some specific tasks than others.

Deleting a single array element

If you want to delete just one array element you can use unset() or alternatively \array_splice().

If you know the value and don’t know the key to delete the element you can use \array_search() to get the key. This only works if the element does not occur more than once, since \array_search returns the first hit only.

unset()

Note that when you use unset() the array keys won’t change. If you want to reindex the keys you can use \array_values() after unset(), which will convert all keys to numerically enumerated keys starting from 0.

Code:

$array = [0 => "a", 1 => "b", 2 => "c"];
unset($array[1]);
          // ↑ Key which you want to delete

Output:

[
    [0] => a
    [2] => c
]

\array_splice() method

If you use \array_splice() the keys will automatically be reindexed, but the associative keys won’t change — as opposed to \array_values(), which will convert all keys to numerical keys.

\array_splice() needs the offset, not the key, as the second parameter.

Code:

$array = [0 => "a", 1 => "b", 2 => "c"];
\array_splice($array, 1, 1);
                   // ↑ Offset which you want to delete

Output:

[
    [0] => a
    [1] => c
]

array_splice(), same as unset(), take the array by reference. You don’t assign the return values of those functions back to the array.

Deleting multiple array elements

If you want to delete multiple array elements and don’t want to call unset() or \array_splice() multiple times you can use the functions \array_diff() or \array_diff_key() depending on whether you know the values or the keys of the elements which you want to delete.

\array_diff() method

If you know the values of the array elements which you want to delete, then you can use \array_diff(). As before with unset() it won’t change the keys of the array.

Code:

$array = [0 => "a", 1 => "b", 2 => "c", 3 => "c"];
$array = \array_diff($array, ["a", "c"]);
                          // └────────┘
                          // Array values which you want to delete

Output:

[
    [1] => b
]

\array_diff_key() method

If you know the keys of the elements which you want to delete, then you want to use \array_diff_key(). You have to make sure you pass the keys as keys in the second parameter and not as values. Keys won’t reindex.

Code:

$array = [0 => "a", 1 => "b", 2 => "c"];
$array = \array_diff_key($array, [0 => "xy", "2" => "xy"]);
                               // ↑           ↑
                               // Array keys which you want to delete

Output:

[
    [1] => b
]

If you want to use unset() or \array_splice() to delete multiple elements with the same value you can use \array_keys() to get all the keys for a specific value and then delete all elements.

\array_filter() method

If you want to delete all elements with a specific value in the array you can use \array_filter().

Code:

$array = [0 => "a", 1 => "b", 2 => "c"];
$array = \array_filter($array, static function ($element) {
    return $element !== "b";
    //                   ↑
    // Array value which you want to delete
});

Output:

[
    [0] => a
    [1] => c
]

It should be noted that unset() will keep indexes untouched, which is what you'd expect when using string indexes (array as hashtable), but can be quite surprising when dealing with integer indexed arrays:

$array = array(0, 1, 2, 3);
unset($array[2]);
var_dump($array);
/* array(3) {
  [0]=>
  int(0)
  [1]=>
  int(1)
  [3]=>
  int(3)
} */

$array = array(0, 1, 2, 3);
array_splice($array, 2, 1);
var_dump($array);
/* array(3) {
  [0]=>
  int(0)
  [1]=>
  int(1)
  [2]=>
  int(3)
} */

So array_splice() can be used if you'd like to normalize your integer keys. Another option is using array_values() after unset():

$array = array(0, 1, 2, 3);

unset($array[2]);
$array = array_values($array);
var_dump($array);
/* array(3) {
  [0]=>
  int(0)
  [1]=>
  int(1)
  [2]=>
  int(3)
} */

unset($array[$index]);

If the index is specified:

$arr = ['a', 'b', 'c'];
$index = 0;    
unset($arr[$index]);  // $arr = ['b', 'c']

If we have value instead of index:

$arr = ['a', 'b', 'c'];

// search the value to find index
// Notice! this will only find the first occurrence of value
$index = array_search('a', $arr);

if($index !== false){
   unset($arr[$index]);  // $arr = ['b', 'c']
}

The if condition is necessary because if index is not found, unset() will automatically delete the first element of the array which is not what we want.

Solutions:

1. To delete one element, use unset():

unset($array[3]);
unset($array['foo']);

2. To delete multiple noncontiguous elements, also use unset():

unset($array[3], $array[5]);
unset($array['foo'], $array['bar']);

3. To delete multiple contiguous elements, use array_splice():

array_splice($array, $offset, $length);

Further explanation:

Using these functions removes all references to these elements from PHP. If you want to keep a key in the array, but with an empty value, assign the empty string to the element:

$array[3] = $array['foo'] = '';

Besides syntax, there's a logical difference between using unset() and assigning '' to the element. The first says This doesn't exist anymore, while the second says This still exists, but its value is the empty string.

If you're dealing with numbers, assigning 0 may be a better alternative. So, if a company stopped production of the model XL1000 sprocket, it would update its inventory with:

unset($products['XL1000']);

However, if it temporarily ran out of XL1000 sprockets, but was planning to receive a new shipment from the plant later this week, this is better:

$products['XL1000'] = 0;

If you unset() an element, PHP adjusts the array so that looping still works correctly. It doesn't compact the array to fill in the missing holes. This is what we mean when we say that all arrays are associative, even when they appear to be numeric. Here's an example:

// Create a "numeric" array
$animals = array('ant', 'bee', 'cat', 'dog', 'elk', 'fox');
print $animals[1];  // Prints 'bee'
print $animals[2];  // Prints 'cat'
count($animals);    // Returns 6

// unset()
unset($animals[1]); // Removes element $animals[1] = 'bee'
print $animals[1];  // Prints '' and throws an E_NOTICE error
print $animals[2];  // Still prints 'cat'
count($animals);    // Returns 5, even though $array[5] is 'fox'

// Add a new element
$animals[ ] = 'gnu'; // Add a new element (not Unix)
print $animals[1];  // Prints '', still empty
print $animals[6];  // Prints 'gnu', this is where 'gnu' ended up
count($animals);    // Returns 6

// Assign ''
$animals[2] = '';   // Zero out value
print $animals[2];  // Prints ''
count($animals);    // Returns 6, count does not decrease

To compact the array into a densely filled numeric array, use array_values():

$animals = array_values($animals);

Alternatively, array_splice() automatically reindexes arrays to avoid leaving holes:

// Create a "numeric" array
$animals = array('ant', 'bee', 'cat', 'dog', 'elk', 'fox');
array_splice($animals, 2, 2);
print_r($animals);
Array
(
    [0] => ant
    [1] => bee
    [2] => elk
    [3] => fox
)

This is useful if you're using the array as a queue and want to remove items from the queue while still allowing random access. To safely remove the first or last element from an array, use array_shift() and array_pop(), respectively.

Two ways for removing the first item of an array with keeping order of the index and also if you don't know the key name of the first item.

Solution #1

// 1 is the index of the first object to get
// NULL to get everything until the end
// true to preserve keys
$array = array_slice($array, 1, null, true);

Solution #2

// Rewinds the array's internal pointer to the first element
// and returns the value of the first array element.
$value = reset($array);
// Returns the index element of the current array position
$key = key($array);
unset($array[$key]);

For this sample data:

$array = array(10 => "a", 20 => "b", 30 => "c");

You must have this result:

array(2) {
  [20]=>
  string(1) "b"
  [30]=>
  string(1) "c"
}

Remove an array element based on a key:

Use the unset function like below:

$a = array(
       'salam',
       '10',
       1
);

unset($a[1]);

print_r($a);

/*

    Output:

        Array
        (
            [0] => salam
            [2] => 1
        )

*/

Remove an array element based on value:

Use the array_search function to get an element key and use the above manner to remove an array element like below:

$a = array(
       'salam',
       '10',
       1
);

$key = array_search(10, $a);

if ($key !== false) {
    unset($a[$key]);
}

print_r($a);

/*

    Output:

        Array
        (
            [0] => salam
            [2] => 1
        )

*/

Edit

If you can't take it as given that the object is in that array you need to add a check:

if(in_array($object,$array)) unset($array[array_search($object,$array)]);

Original Answer

if you want to remove a specific object of an array by reference of that object you can do following:

unset($array[array_search($object,$array)]);

Example:

<?php
class Foo
{
    public $id;
    public $name;
}

$foo1 = new Foo();
$foo1->id = 1;
$foo1->name = 'Name1';

$foo2 = new Foo();
$foo2->id = 2;
$foo2->name = 'Name2';

$foo3 = new Foo();
$foo3->id = 3;
$foo3->name = 'Name3';


$array = array($foo1,$foo2,$foo3);
unset($array[array_search($foo2,$array)]);

echo '<pre>';
var_dump($array);
echo '</pre>';
?>

Result:

array(2) {
[0]=>
    object(Foo)#1 (2) {
        ["id"]=>
        int(1)
        ["name"]=>
        string(5) "Name1"
    }
[2]=>
    object(Foo)#3 (2) {
        ["id"]=>
        int(3)
        ["name"]=>
        string(5) "Name3"
    }
}

Note that if the object occures several times it will only be removed the first occurence!

I came here because I wanted to see if there was a more elegant solution to this problem than using unset($arr[$i]). To my disappointment these answers are either wrong or do not cover every edge case.

Here is why array_diff() does not work. Keys are unique in the array, while elements are not always unique.

$arr = [1,2,2,3];

foreach($arr as $i => $n){
    $b = array_diff($arr,[$n]);
    echo "\n".json_encode($b);
}

Results...

[2,2,3]
[1,3]
[1,2,2] 

If two elements are the same they will be remove. This also applies for array_search() and array_flip().

I saw a lot of answers with array_slice() and array_splice(), but these functions only work with numeric arrays. All the answers I am aware if here does not answer the question, and so here is a solution that will work.

$arr = [1,2,3];

foreach($arr as $i => $n){
    $b = array_merge(array_slice($arr,0,$i),array_slice($arr,$i+1));
    echo "\n".json_encode($b);
}

Results...

[2,3];
[1,3];
[1,2];

Since unset($arr[$i]) will work on both associative array and numeric arrays this still does not answer the question.

This solution is to compare the keys and with a tool that will handle both numeric and associative arrays. I use array_diff_uassoc() for this. This function compares the keys in a call back function.

$arr = [1,2,2,3];
//$arr = ['a'=>'z','b'=>'y','c'=>'x','d'=>'w'];
foreach($arr as $key => $n){
    $b = array_diff_uassoc($arr, [$key=>$n], function($a,$b) {
        if($a != $b){
            return 1;
        }
    });
    echo "\n".json_encode($b);
}    

Results.....

[2,2,3];
[1,2,3];
[1,2,2];

['b'=>'y','c'=>'x','d'=>'w'];
['a'=>'z','c'=>'x','d'=>'w'];
['a'=>'z','b'=>'y','d'=>'w'];
['a'=>'z','b'=>'y','c'=>'x'];