How to remove duplicate values ​​from an array in php

During development, we often encounter situations where we need to remove duplicate values ​​from an array. As a popular server-side scripting language, PHP provides a wealth of functions and methods for operating arrays. This article will introduce several commonly used methods to remove duplicate values ​​from arrays in PHP.

Method 1: array_unique()

array_unique() is one of the most commonly used methods in PHP to remove duplicate values ​​from an array. This function returns a new array containing only the unique values ​​in the input array. The following is an example of use:

$array = array("apple", "banana", "cherry", "banana", "orange", "apple");
$newArray = array_unique($array);
print_r($newArray);

The output result of the above code is:

Array
(
    [0] => apple
    [1] => banana
    [2] => cherry
    [4] => orange
)

As can be seen from the output result, the array_unique() function removes duplicates in the original array value and returns a new array. It should be noted that when this function removes duplicates, it determines whether there are duplicates based on the value, not the key.

Method 2: foreach loop to remove duplicates

In addition to using the array_unique() function, we can also loop through the array and remove duplicate values. The following is an example of using foreach loop to remove duplicates:

$array = array("apple", "banana", "cherry", "banana", "orange", "apple");
$newArray = array();
foreach ($array as $value) {
    if (!in_array($value, $newArray)) {
        $newArray[] = $value;
    }
}
print_r($newArray);

The output result of the above code is the same as method one. It should be noted that when using the in_array function to determine whether a value is repeated, you need to use the ! negation sign to negate it to ensure that non-repeating values ​​are added to the new in the array.

Method 3: array_flip()

array_flip()The function can exchange the keys and values ​​in the array to achieve the effect of deduplication. Before deduplication, we can use array_flip() to exchange keys and values ​​first, and then restore the array through array_flip(). The following is an example:

$array = array("apple", "banana", "cherry", "banana", "orange", "apple");
$newArray = array_flip(array_flip($array));
print_r($newArray);

The output result of the above code is the same as method one and method two. It should be noted that if there are duplicate values ​​in the original array, the subsequent values ​​will be lost after exchanging the key-value pairs, leaving only the last one. Therefore, when using array_flip(), you need to first use array_flip() to remove duplicate key values, and then use array_flip() to restore the original array. .

In short, the above are three methods commonly used in PHP to remove duplicate values ​​from arrays. Depending on actual needs, choosing different methods can improve program efficiency and make the code more concise and easy to understand.

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