PHP array_key_exists: Usage Guide & Examples

The array_key_exists function is used to check if a specific key exists in an array. Its syntax is as follows:

array_key_exists($key, $array)

其中，$key为要检查的键名，$array为要检查的数组。

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$colors = array("red" => "apple", "yellow" => "banana", "green" => "pear");

if (array_key_exists("red", $colors)) {
    echo "Red color exists in the array";
} else {
    echo "Red color does not exist in the array";
}

In the example above, we first created an associative array $colors containing colors and fruits. Then we used the array_key_exists function to check if the key “red” exists in the array. If it does, we output “Red color exists in the array”, otherwise we output “Red color does not exist in the array”.