PHP array unique value

$old_array=array("Mango","Banana","Orange","Banana"); 
$new_array=array_unique($old_array); 

$old_array=array("Mango","Banana","Orange","Banana"); 
if(count($old_array) != count(array_unique($old_array))){
echo " Not Unique, there are duplicate elements ";	
}else{
echo " No duplicate elements ";
}

Not Unique, there are duplicate elements 

Getting the duplicate elements

$old_array=array("Mango","Banana","Orange","Banana"); 
$new_array=array_unique($old_array); 

// What is not common in both arrays ( keys also considered ) ///

$duplicate=array_diff_assoc($old_array,$new_array);
while (list ($key, $val) = each ($duplicate)) {
echo "$key -> $val <br>";
}

3 -> Banana

Example 2: Preserving Keys with Unique Values

The array_unique() function removes duplicate values but resets the keys by default. To preserve the keys, use the second parameter:

$arr = ["a" => "apple", "b" => "banana", "c" => "apple"];
$new_array = array_unique($arr, SORT_REGULAR);
print_r($new_array); 
// Output: Array ( [a] => apple [b] => banana )

Example 3: Removing Duplicates in Multidimensional Arrays

Using array_unique() in multidimensional arrays can be tricky. Here's how to remove duplicate sub-arrays:

$arr = [
    ['name' => 'John', 'age' => 25],
    ['name' => 'John', 'age' => 25],
    ['name' => 'Jane', 'age' => 30]
];
$new_array = array_map('unserialize', array_unique(array_map('serialize', $arr)));
print_r($new_array);

Array ( [0] => Array ( [name] => John [age] => 25 ) [2] => Array ( [name] => Jane [age] => 30 ) )

Use Case: Checking for Uniqueness Across Multiple Fields

In some cases, you may want to ensure uniqueness across multiple fields in an array of associative arrays.

$people = [
    ['name' => 'Alice', 'email' => 'alice@example.com'],
    ['name' => 'Bob', 'email' => 'bob@example.com'],
    ['name' => 'Alice', 'email' => 'alice@example.com']
];
$unique_people = array_map('unserialize', array_unique(array_map('serialize', $people)));
print_r($unique_people);

Array ( [0] => Array ( [name] => Alice [email] => alice@example.com ) [1] => Array ( [name] => Bob [email] => bob@example.com ) )

Example 4: Performance Consideration for Large Arrays

When working with large arrays, removing duplicates can be resource-intensive. Consider combining *array_flip()* with array_keys() for faster execution:

$arr = array_fill(0, 100000, 'test');
$unique = array_keys(array_flip($arr));
print_r($unique);

Subhendu Mohapatra

Author & Instructor at plus2net

I write and maintain practical tutorials on Python, PHP, SQL, JavaScript, HTML, jQuery, and web development at plus2net. The tutorials focus on clear explanations, working examples, and code that readers can test and adapt while learning.

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