How to determine if an element is in an array in php

In PHP programming, the data type of array is often used. Determining whether an element is in an array is a very common operation. This article will introduce a variety of methods to determine whether elements are in an array, hoping to be helpful to PHP beginners.

1. Use the in_array function

The in_array function is a way to quickly determine whether an element is in an array. The function prototype is:

bool in_array ( mixed $needle , array $haystack [, bool $strict = FALSE ] )

where $needle is the element to be found and $haystack is the target Array, $strict is whether to enable type checking. The default is FALSE, which means no type checking.

The following is an example:

$arr = array("apple", "banana", "orange");
if (in_array("banana", $arr)) {
    echo "找到了！";
} else {
    echo "没找到。";
}

The output result is: Found!

2. Use the array_search function

The array_search function is also a function used to find whether an element is in an array. However, it returns the key name of the element rather than a Boolean value. The function prototype is:

mixed array_search ( mixed $needle , array $haystack [, bool $strict = FALSE ] )

where $needle is the element to be found and $haystack is the target Array, $strict is whether to enable type checking. The default is FALSE, which means no type checking.

The following is an example:

$arr = array("apple", "banana", "orange");
$key = array_search("banana", $arr);
if ($key !== false) {
    echo "找到了！键名是：" . $key;
} else {
    echo "没找到。";
}

The output result is: Found! The key name is: 1

3. Use isset function

isset function is a built-in function in PHP, used to detect whether the variable is set and non-NULL. We can use the isset function and the key name of the array to determine whether an element is in the array. Sample code:

$arr = array("apple", "banana", "orange");
if (isset($arr[1])) {
    echo "找到了！";
} else {
    echo "没找到。";
}

The output result is: Found!

4. Use the array_key_exists function

The array_key_exists function is a function that checks whether the specified key name exists in the array. The function prototype is:

bool array_key_exists (mixed $key, array $array)

Among them, $key is the key name to be found, and $array is the target array.

Sample code:

$arr = array("apple", "banana", "orange");
if (array_key_exists(1, $arr)) {
    echo "找到了！";
} else {
    echo "没找到。";
}

The output result is: Found!

5. Use the indexOf function

The indexOf function is a custom function used to check whether the element is in the array. The function prototype is:

function indexOf($array, $search_value)
{

foreach($array as $key => $value) {
    if($value === $search_value) {
        return $key;
    }
}
return false;

}

Among them, $array is the target array and $search_value is the target array. The element to find.

Sample code:

$arr = array("apple", "banana", "orange");
$key = indexOf($arr, "banana");
if ($key !== false) {
    echo "找到了！键名是：" . $key;
} else {
    echo "没找到。";
}

The output result is: Found! The key name is: 1

The above are several methods in PHP to determine whether an element is in an array, among which in_array and array_search are the most commonly used methods. In actual use, you can choose according to your own needs.

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