How to use in_array() to determine whether a value exists in an array

In PHP, we can use the in_array() function to determine whether a value exists in an array. This function accepts two parameters: the value to be found and the array to search. Returns True if the value exists in the array; False otherwise.

The following is a sample code:

$fruits = array("apple", "banana", "orange", "kiwi");

if (in_array("apple", $fruits)) {
    echo "找到了苹果！";
} else {
    echo "未找到苹果。";
}

The above code will output "Apple found!" because "apple" exists in the $fruits array.

We can also set the third parameter of the in_array() function to True to force type checking. This means that if the value you are looking for and the value in the array are of different data types (such as string and integer), the function will return False. Here is an example:

$fruits = array("1", 2, "3", 4);

if (in_array(3, $fruits, True)) {
    echo "找到了3！";
} else {
    echo "未找到3。";
}

The above code will output "3 not found." because although there is a string with the value "3" in the $fruits array, the value to be found is the integer 3.

In addition to the in_array() function, we can also use the array_search() function to find the position of a value in the array. This function also accepts two parameters: the value to be found and the array to search. If the value exists in the array, returns the key name of the value in the array; otherwise, returns False. Here is an example:

$fruits = array("apple", "banana", "orange", "kiwi");

$key = array_search("banana", $fruits);

if ($key !== False) {
    echo "找到了香蕉，它在数组中的位置是$key。";
} else {
    echo "未找到香蕉。";
}

The above code will output "Found banana, its position in the array is 1.", because the key name of "banana" is 1.

In short, finding values ​​in an array is a very common operation in PHP. The in_array() and array_search() functions are the two most basic methods we can use, but there are many other built-in functions that make it easier for us to find values ​​in arrays. No matter which method is used, we must remember to check the return value of the function to determine whether we found the required value.

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