How to determine if a value is in an array in php

In PHP development, we often need to determine whether a value is in an array. If a value is in the array, we can directly use the in_array() function to determine, but if a value is not in the array, how to determine? This article will introduce various methods to determine whether a value is in an array.

Method 1: Use in_array() function to invert

The in_array() function can determine whether a value is in the array. If not, it returns false.

We can use this feature to determine that a value is not in the array.

Code example:

$needle = 'apple';
$fruits = ['banana', 'orange', 'grape'];

if (!in_array($needle, $fruits)) {
    echo $needle . ' is not in the fruits array.';
}

Output result:

apple is not in the fruits array.

Method 2: Use array_search() function

array_search() function can search for an item in the array value and returns the key name of the value. If the value is not in the array, returns false.

We can use this feature to determine that a value is not in the array.

Code example:

$needle = 'apple';
$fruits = ['banana', 'orange', 'grape'];

if (array_search($needle, $fruits) === false) {
    echo $needle . ' is not in the fruits array.';
}

Output result:

apple is not in the fruits array.

Method 3: Use the array_diff() function

array_diff() function can calculate two or Difference of multiple arrays, that is, it can find values ​​that are not in the array.

We can calculate the difference between the value to be judged as an array with only one element and the original array. If the result of the difference set is an empty array, it means that the value to be judged is not in the original array.

Code example:

$needle = 'apple';
$fruits = ['banana', 'orange', 'grape'];

if (empty(array_diff([$needle], $fruits))) {
    echo $needle . ' is not in the fruits array.';
}

Output result:

apple is not in the fruits array.

Method 4: Use the count() function

We can use the count() function to obtain the contents of the array The number of elements is used to determine the number of times the value to be found appears in the original array. If the number is 0, it means that the value is not in the original array.

Code example:

$needle = 'apple';
$fruits = ['banana', 'orange', 'grape'];

if (count(array_keys($fruits, $needle)) === 0) {
    echo $needle . ' is not in the fruits array.';
}

Output result:

apple is not in the fruits array.

Method 5: Use foreach loop

We can use foreach loop to traverse the array and find the items to be judged Whether the value is in the array. If the value to be judged is not found after traversing the array, it means that the value is not in the array.

Code example:

$needle = 'apple';
$fruits = ['banana', 'orange', 'grape'];

$found = false;
foreach ($fruits as $fruit) {
    if ($fruit === $needle) {
        $found = true;
        break;
    }
}

if (!$found) {
    echo $needle . ' is not in the fruits array.';
}

Output result:

apple is not in the fruits array.

Method 6: Use array_key_exists() function

If the key name of the array is a string, we You can use the array_key_exists() function to determine whether a key exists in the array.

Code example:

$needle = 'apple';
$fruits = ['banana' => 1, 'orange' => 1, 'grape' => 1];

if (!array_key_exists($needle, $fruits)) {
    echo $needle . ' is not in the fruits array.';
}

Output result:

apple is not in the fruits array.

Conclusion

This article introduces a variety of methods to determine that a value is not in the array. Each method has its advantages and disadvantages, and we can choose the most suitable method according to the specific situation. In actual development, we can also use these techniques flexibly in combination with specific scenarios to improve development efficiency and code quality.

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