How to determine whether a value belongs to an array in php

In PHP, there are several ways to determine whether a value belongs to an array. This article will introduce these methods and give sample code.

1. in_array() function

in_array() function can check whether a value is in the array and returns true if it is, otherwise it returns false. The syntax of this function is as follows:

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

Where $needle is the value to be found, $haystack is the array, $strict is an optional parameter, if set to true, type checking will be performed during comparison. Here is an example:

$my_array = array("apple", "banana", "orange");
if (in_array("apple", $my_array)) {
    echo "apple is in the array";
} else {
    echo "apple is not in the array";
}

2. array_search() function

array_search() function searches for a value in an array and returns its key if not found Return false. The syntax of this function is as follows:

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

Where $needle is the value to be found, $haystack is the array, $strict is an optional parameter, if set to true, type checking will be performed during comparison. Here is an example:

$my_array = array("apple", "banana", "orange");
$key = array_search("banana", $my_array);
if ($key !== false) {
    echo "banana is at index $key";
} else {
    echo "banana is not in the array";
}

3. isset() function

isset() function can check whether a value exists and returns true if it exists, otherwise it returns false. When determining whether a value is in an array, you can use the value as the key of the array. Here is an example:

$my_array = array("apple" => 1, "banana" => 2, "orange" => 3);
if (isset($my_array["apple"])) {
    echo "apple is in the array";
} else {
    echo "apple is not in the array";
}

4. array_key_exists() function

array_key_exists() function can check whether a key exists in the array and returns true if it exists, otherwise it returns false. The following is an example:

$my_array = array("apple" => 1, "banana" => 2, "orange" => 3);
if (array_key_exists("apple", $my_array)) {
    echo "apple is a key in the array";
} else {
    echo "apple is not a key in the array";
}

5. The difference between in_array() and array_search() functions

Although both in_array() and array_search() functions can check whether a value is in array, but their return values ​​are different. The in_array() function returns true or false, while the array_search() function may return a numeric value or false. For example, the following code will output "banana is at index 1":

$my_array = array("apple", "banana", "orange");
$key = array_search("banana", $my_array);
if ($key !== false) {
    echo "banana is at index $key";
} else {
    echo "banana is not in the array";
}

6. Using a foreach loop

The last way to check whether a value is in the array is Use a foreach loop to iterate through each value in the array and compare them to see if they are equal to the value you are looking for. Here is an example:

$my_array = array("apple", "banana", "orange");
$found = false;
foreach ($my_array as $value) {
    if ($value == "banana") {
        $found = true;
        break;
    }
}
if ($found) {
    echo "banana is in the array";
} else {
    echo "banana is not in the array";
}

The above are several ways to determine whether a value belongs to an array in PHP. Using these methods makes it easier for us to work with arrays.

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