PHP array determines whether it exists

In PHP, we often need to determine whether an array contains an element. This can be easily achieved using some built-in functions. Below we will introduce some methods to determine whether an array element exists.

1. Use the in_array function
The in_array() function can be used to determine whether a value exists in an array. Its syntax is as follows:

bool in_array ( mixed $needle , array $haystack [, bool $strict = FALSE ] )

Among them, $needle is the value to be found, $haystack is the array to be found, and $strict indicates whether type checking is enabled. For example, the following code checks whether array $arr contains element 3:

$arr = array(1, 2, 3, 4);
if (in_array(3, $arr)) {
    echo "元素3存在于数组中";
} else {
    echo "元素3不存在于数组中";
}

The above code will output:

元素3存在于数组中

2. Use the array_key_exists function
array_key_exists() function is used to check an array Whether the specified key exists. Its syntax is as follows:

bool array_key_exists ( mixed $key , array $array )

Among them, $key is the key to be searched, and $array is the array to be searched. For example, the following code checks whether the key "Peter" exists in the array $age:

$age = array("Peter"=>35, "Ben"=>37, "Joe"=>43);
if (array_key_exists("Peter", $age)) {
    echo "键值Peter存在于数组中";
} else {
    echo "键值Peter不存在于数组中";
}

The above code will output:

键值Peter存在于数组中

3. Use the isset function
isset() function is used to check an Whether the variable has been defined and the value is not NULL. When working with arrays, the isset() function is usually used to check whether an element in an array exists. For example, the following code checks whether the array $colors contains subscript 2:

$colors = array("red", "green", "blue");
if (isset($colors[2])) {
    echo "元素2存在于数组中";
} else {
    echo "元素2不存在于数组中";
}

The above code will output:

元素2存在于数组中

Summary
In PHP, determine whether an array contains an element, Commonly used methods include in_array(), array_key_exists() and isset() functions. You can choose the method that suits your needs according to the actual situation.

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