PHP determines whether a string is in an array

In PHP development, it is often necessary to determine whether a string is in an array. This is a very common need, especially when working with form data. In this article, we will introduce several ways to determine whether a string is in an array in PHP.

1. Use in_array()

In PHP, you can use the in_array() function to determine whether a value is in an array. This function accepts two parameters: the value to be found and the array to be found. Returns true if the value is found, false otherwise.

The following is how to use the in_array() function:

// 定义一个数组
$array = array('apple', 'orange', 'banana', 'mango');

// 判断 'apple' 是否在数组中
if (in_array('apple', $array)) {
    echo 'apple 在数组中';
} else {
    echo 'apple 不在数组中';
}

Output:

apple 在数组中

2. Use array_search()

array_search() function and in_array The () function is similar and is also used to determine whether a value is in an array. The difference is that if the value is found, the array_search() function returns the key name of the value in the array, otherwise it returns false.

The following is how to use the array_search() function:

// 定义一个数组
$array = array('apple', 'orange', 'banana', 'mango');

// 查找 'orange' 在数组中的位置
$key = array_search('orange', $array);

if ($key !== false) {
    echo "orange 在数组中的位置是：$key";
} else {
    echo 'orange 不在数组中';
}

Output:

orange 在数组中的位置是：1

3. Use in_array() and strict parameters

in_array() The function has an optional third parameter strict, which is used to specify whether to force type comparison. By default, the in_array() function uses relaxed comparison mode.

The following is an example:

$array = array(1, 'apple', true);

// 宽松比较，返回 true
if (in_array('1', $array)) {
    echo "'1' 在数组中";
} else {
    echo "'1' 不在数组中";
}

echo '<br>';

// 强制类型比较，返回 false
if (in_array('1', $array, true)) {
    echo "'1' 在数组中";
} else {
    echo "'1' 不在数组中";
}

Output:

'1' 在数组中
'1' 不在数组中

4. Using array_key_exists()

In addition to determining whether a value is in the array, sometimes we You also need to determine whether a key is in the array. This can be done using the array_key_exists() function. This function accepts two parameters: the key to be searched and the array to be searched. Returns true if the key is found, false otherwise.

The following is how to use the array_key_exists() function:

// 定义一个数组
$array = array('username' => 'jack', 'email' => 'jack@example.com', 'phone' => '123456789');

// 判断 'username' 是否在数组中
if (array_key_exists('username', $array)) {
    echo 'username 在数组中';
} else {
    echo 'username 不在数组中';
}

Output:

username 在数组中

5. Using isset() and array keys

in PHP The isset() function can be used to check whether a variable has been set and is not null. In an array, we can use the array key as a variable name to determine whether a key is in the array.

The following is an example:

// 定义一个数组
$array = array('username' => 'jack', 'email' => 'jack@example.com', 'phone' => '123456789');

// 判断 'username' 是否在数组中
if (isset($array['username'])) {
    echo 'username 在数组中';
} else {
    echo 'username 不在数组中';
}

Output:

username 在数组中

Summary

In PHP development, determining whether a string is in an array is a very common needs. We can use in_array(), array_search(), array_key_exists(), isset() and other functions to achieve this.

Using the in_array() and array_search() functions, you can check whether a value is in an array. Using the array_key_exists() function, you can check if a key is in an array. Using the isset() function with an array key you can check if the key is in the array.

According to specific business needs, choose the appropriate method to determine whether the string is in the array.

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