php delete identical elements

When performing data processing, sometimes it is necessary to delete the same elements in the array. If you are using PHP language, then you can use some built-in functions and tricks to delete identical elements from an array. This article will introduce these techniques and functions to you, as well as some precautions.

1. Use the array_unique() function

PHP provides a function called array_unique(), which can be used to delete the same elements in the array. This function returns a new array with all duplicate elements removed. This function is very convenient and only requires one line of code to complete the data deduplication task.

Sample code:

$arr = array('a', 'b', 'c', 'a', 'd', 'e', 'b');
$arr = array_unique($arr);
print_r($arr);

Output result:

Array
(
    [0] => a
    [1] => b
    [2] => c
    [4] => d
    [5] => e
)

2. Use loops and conditional statements

If you don’t want to use the array_unique() function, you can also You can use loops and conditional statements to manually remove duplicate elements from an array. The specific steps are as follows:

• Define an empty new array $newArr;
• Loop through the original array $arr, and use each element to find whether the same element exists in the new array $newArr , if it does not exist, add the element to the new array;
• If the same element exists, skip the element;
• After the loop ends, $newArr does not contain duplicate elements new array.

Sample code:

$arr = array('a', 'b', 'c', 'a', 'd', 'e', 'b');
$newArr = array();
foreach ($arr as $key => $value) {
    if (!in_array($value, $newArr)) {
        $newArr[] = $value;
    }
}
print_r($newArr);

Output result:

Array
(
    [0] => a
    [1] => b
    [2] => c
    [4] => d
    [5] => e
)

3. Use array_flip() function and array_keys() function

in PHP The array_flip() function swaps the keys and values ​​of an array while removing duplicate elements. We can exchange the keys and values ​​of the array and then use the array_keys() function to obtain all key values ​​to achieve the effect of deleting duplicate elements.

Sample code:

$arr = array('a', 'b', 'c', 'a', 'd', 'e', 'b');
$arr = array_flip($arr);
$arr = array_keys($arr);
print_r($arr);

Output result:

Array
(
    [0] => a
    [1] => b
    [2] => c
    [3] => d
    [4] => e
)

Things to note:

• If they exist in the array, they will be treated as the same Values ​​such as empty strings, 0 and null are also deleted.
• If you are using an array with key names, the key names are not retained when using the array_unique() function. If you want to retain the key name, you need to use manual deletion;
• When the elements in the array are objects, different objects cannot be compared, so when there are multiple objects in the array, they Will not be considered a duplicate element.
• For large arrays and multi-dimensional arrays, deleting duplicate elements in the array may consume a lot of time and memory. You need to pay attention to the performance and efficiency of the program.

Summary:

PHP provides some convenient built-in functions and tricks for deleting identical elements in an array. You can choose to use the array_unique() function, loops, and conditional statements to achieve this. Different methods have their own advantages and applicable scenarios, and you need to choose according to the actual situation. No matter which method you choose, pay attention to the performance and efficiency of the program and make reasonable use of techniques and functions to make the program more concise and efficient.

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