PHP determines whether it is in the array

In PHP programming, determining whether an element is in an array is a very common operation. Therefore, this article will introduce how to determine whether an element is in an array in PHP.

1. Use the in_array() function

PHP provides an in_array() function that can check whether an element is in an array. The usage of this function is as follows:

in_array($needle, $haystack);

Among them, $needle is the element to be found, and $haystack is the array to be found. The function returns a Boolean value indicating whether the element is in the array. Returns true if the element is in the array; returns false if the element is not in the array.

The following is an example of using the in_array() function:

$array = array("apple", "banana", "cherry");
if (in_array("banana", $array)) {
   echo "在数组中";
} else {
   echo "不在数组中";
}

In this example, $array is an array containing three elements. We use the in_array() function to check whether it exists Element "banana". Because "banana" is in the array, the output is "in array".

2. Use the array_search() function

Similar to the in_array() function, PHP also provides an array_search() function, which can also be used to find whether an element is in an array. The usage of this function is as follows:

array_search($needle, $haystack);

Among them, $needle is the element to be found, and $haystack is the array to be found. The function returns the key of an element, or false if the element is not in the array.

The following is an example of using the array_search() function:

$array = array("apple", "banana", "cherry");
$key = array_search("banana", $array);
if ($key !== false) {
   echo "在数组中，键名是" . $key;
} else {
   echo "不在数组中";
}

In this example, $array is an array containing three elements. We use the array_search() function to find whether it exists Element "banana". Because "banana" is in the array, the output is "In the array, the key is 1". Note that because the key for "banana" is 1 (counting starts from 0), the key in the output is 1.

3. The difference between using in_array() and array_search()

Although both in_array() and array_search() functions can be used to find whether an element is in an array, they are There are some differences between:

1. in_array() returns true or false, array_search() returns the key name of the element or false.
2. If there are multiple elements with equal values ​​in the array, in_array() will only return true or false, and array_search() will return the key name of the first element.
3. The processing efficiency of in_array() is higher than array_search(), because it only needs to determine whether the element exists and does not need to obtain the key name of the element.

4. Use the isset() function

In addition to the above two functions, you can also use the isset() function to determine whether an element exists in the array. The usage of this function is as follows:

isset($array[$key]);

Among them, $array is the array to be searched, and $key is the key name of the element to be searched. This function returns a Boolean value indicating whether the element is in the array. Returns true if the element is in the array; returns false if the element is not in the array.

The following is an example of using the isset() function:

$array = array("apple", "banana", "cherry");
if (isset($array[1])) {
   echo "在数组中";
} else {
   echo "不在数组中";
}

In this example, $array is an array containing three elements. We use the isset() function to find the index Whether the element of 1 exists. Because the element at index 1 is "banana", the output is "in array".

Summary

In PHP programming, judging whether an element is in an array is a very basic operation and a common requirement. The above introduces the methods in PHP to determine whether an element is in an array, including the in_array(), array_search() and isset() functions. In actual programming, we can choose which method to use based on specific scenarios.

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