How to determine whether an array has a value in php

In PHP, to determine whether an array has a value, you can use the array_key_exists() function and isset() function. Let us learn more about the usage of these two functions.

1. array_key_exists()

array_key_exists() function is used to determine whether the specified key name exists in an array. If it exists, it returns true, otherwise it returns false. The following is the syntax of this function:

bool array_key_exists ( mixed $key , array $array )

Among them, $key represents the key name to be judged, and $array represents the array to be judged.

The following is an example:

$arr = array('a' => 1, 'b' => 2, 'c' => 3);
if (array_key_exists('a', $arr)) {
    echo '存在';
} else {
    echo '不存在';
}

The output result is: existence

2. isset()

isset() function is used to determine whether a variable It has been declared and assigned a value. If it is, it returns true, otherwise it returns false. When judging an array, if the specified element value is null, the isset() function will return false. The following is the syntax of this function:

bool isset ( mixed $var [, mixed $... ] )

When judging array elements, you can use the following two methods:

1. Use the isset() function to directly judge whether the element exists, as shown below ：

$arr = array('a' => 1, 'b' => null, 'c' => 3);
if (isset($arr['a'])) {
    echo '存在';
} else {
    echo '不存在';
}

The output result is: exists

if (isset($arr['b'])) {
    echo '存在';
} else {
    echo '不存在';
}

The output result is: does not exist

2. First use the array_key_exists() function to determine whether the element exists, and then Use the isset() function to determine whether the value of the element is null, as shown below:

$arr = array('a' => 1, 'b' => null, 'c' => 3);
if (array_key_exists('a', $arr) && isset($arr['a'])) {
    echo '存在';
} else {
    echo '不存在';
}

The output result is: exists

if (array_key_exists('b', $arr) && isset($arr['b'])) {
    echo '存在';
} else {
    echo '不存在';
}

The output result is: does not exist

Summary

The above is how PHP determines whether an array has a value. You can choose according to your own needs. In actual development, it is recommended to use the isset() function to determine whether an array element exists, because this function is fast and can prevent undefined index errors. Of course, when determining whether a key exists, you can use the array_key_exists() function.

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