PHP query whether array includes key value

In PHP development, querying whether an array contains a certain key value is a frequently faced problem. This article will introduce some methods to determine whether an array contains a certain key value.

1. Use the in_array function
The in_array function can determine whether a value is in the array, but this function cannot determine whether the key value is in the array alone, because by default the in_array function only determines the key-value correspondence Whether the value is in the array. However, we can use the array_keys function in the array to get the key name of the array, and then use the in_array function to determine whether the specified key value is in the key name.

The following is a sample code:

$array = array('foo' => 'bar', 'bar' => 'foo');
if (in_array('foo', array_keys($array))) {
    echo "包含键值foo";
} else {
    echo "不包含键值foo";
}

The running result is: Contains the key value foo

2. Use the array_key_exists function
The array_key_exists function can determine whether a key name is in the array exists, returns true if it exists, otherwise returns false.

The following is a sample code:

$array = array('foo' => 'bar', 'bar' => 'foo');
if (array_key_exists('foo', $array)) {
    echo "包含键值foo";
} else {
    echo "不包含键值foo";
}

The running result is: Contains the key value foo

It should be noted that when using the array_key_exists function to determine whether the key value is in the array, only You need to pass in the key name to be judged, not the value corresponding to the key name.

3. Use isset function
isset function is similar to array_key_exists function, but more strict. It not only determines whether the key name exists in the array, but also determines whether the value corresponding to the key name is null. If the value corresponding to the key name is not null, it returns true, otherwise it returns false.

The following is a sample code:

$array = array('foo' => 'bar', 'bar' => 'foo');
if (isset($array['foo'])) {
    echo "包含键值foo";
} else {
    echo "不包含键值foo";
}

The running result is: Contains the key value foo

4. Use the array_search function
array_search function to search for the specified value in the array, Returns its corresponding key name. You can determine whether the array contains the specified key value by determining whether the return value of the array_search function is false.

The following is a sample code:

$array = array('foo' => 'bar', 'bar' => 'foo');
if (array_search('foo', $array) !== false) {
    echo "包含键值foo";
} else {
    echo "不包含键值foo";
}

The running result is: containing the key value foo

It should be noted that if there are multiple key names in the array, the corresponding values ​​​​are Specify the value, and the array_search function only returns the value of the first key name.

To sum up, the above four methods can be used to determine whether an array contains a certain key name. According to different scenarios and needs, we can choose the appropriate method to determine whether the array contains the specified key value.

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