PHP query whether the value is in the array

PHP provides some built-in functions to query whether a value exists in an array. In development, we often need to determine whether a certain value exists in an array for further processing. This article will explore some commonly used PHP built-in functions to deal with this problem.

1. in_array() function

The in_array() function is one of the most basic functions in PHP and can be used to determine whether a value exists in an array. The syntax is as follows:

in_array($value, $array)

Among them, $value is the value to be found, and $array is the array to be found in. The function returns TRUE if the value is found, FALSE otherwise.

For example, if we want to determine whether the number 5 exists in the array [1,2,3,4,5], we can use the following code:

$array = [1,2,3,4,5];
if (in_array(5, $array)) {
    echo '数字5在数组中存在';
} else {
    echo '数字5在数组中不存在';
}

This code will output: Number 5 exists in the array. Because the number 5 does exist in the array.

2. array_search() function

array_search() function is similar to the in_array() function, but the difference is that this function returns the found key name instead of TRUE or FALSE.

The syntax is as follows:

array_search($value, $array)

Among them, $value is the value to be searched, and $array is the array to be searched in. If the value is found, the function returns the key name corresponding to the value, otherwise it returns FALSE.

For example, if we want to find the key name of the number 5 in the array [1,2,3,4,5], we can use the following code:

$array = [1,2,3,4,5];
$key = array_search(5, $array);
if ($key !== false) {
    echo '数字5在数组中的键名为' . $key;
} else {
    echo '数字5在数组中不存在';
}

This code will output: number The key name of 5 in the array is 4. Because the number 5 is at index 4 in the array.

3. isset() function

isset() function can be used to determine whether a key name in an array exists. The syntax is as follows:

isset($array[$key])

Among them, $array is the array to be queried, and $key is the key name to be queried. If the key exists in the array, the function returns TRUE, otherwise it returns FALSE.

For example, if we want to query whether the key name 'a' in the array $arr exists, we can use the following code:

$arr = ['a'=>1, 'b'=>2, 'c'=>3];
if (isset($arr['a'])) {
    echo '键名a在数组中存在';
} else {
    echo '键名a在数组中不存在';
}

This code will output: The key name a exists in the array. Because there is indeed an element with the key name 'a' in the array $arr.

4. array_key_exists() function

array_key_exists() function is similar to isset() function, but the difference is that this function can only be used to check the key name in the array Whether it exists, but cannot check whether the value corresponding to the key name exists.

The syntax is as follows:

array_key_exists($key, $array)

Among them, $key is the key name to be queried, and $array is the array to be queried. If the key exists in the array, the function returns TRUE, otherwise it returns FALSE.

For example, if we want to query whether the key name 'a' in the array $arr exists, we can use the following code:

$arr = ['a'=>1, 'b'=>2, 'c'=>3];
if (array_key_exists('a', $arr)) {
    echo '键名a在数组中存在';
} else {
    echo '键名a在数组中不存在';
}

This code will output: The key name a exists in the array. Because there is indeed an element with the key name 'a' in the array $arr.

Summary

The above are some commonly used built-in functions in PHP to query whether a value exists in an array. Depending on the specific needs and circumstances, we may sometimes need to use more than one method to conduct an inspection. Although these functions look simple, their role in development is very important. I hope this article can help readers solve the problem of querying whether a value is in an array in PHP, and gain more experience and skills in practice.

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