The in_array() function in PHP checks if a value exists in an array. It returns true if the value is found, and false if it is not.

Syntax:

in_array($needle, $haystack, $strict);

• $needle: The value to search for in the array.
• $haystack: The array in which to search for the value.
• $strict (optional): If set to true, it will also check the types of the $needle and array elements. If false (default), it will only check the value, ignoring types.

Examples:

Example 1: Basic usage

$fruits = ["apple", "banana", "cherry"];

if (in_array("banana", $fruits)) {
    echo "Banana is in the array.";
} else {
    echo "Banana is not in the array.";
}

Output:

Banana is in the array.

Example 2: Strict comparison

$numbers = [1, 2, 3, "4"];

if (in_array(4, $numbers, true)) {  // strict comparison enabled
    echo "4 is in the array.";
} else {
    echo "4 is not in the array.";
}

Output:

4 is not in the array.  // because 4 as an integer is different from "4" as a string

Example 3: Searching for a string in an array of strings

$names = ["John", "Jane", "Doe"];

if (in_array("Jane", $names)) {
    echo "Jane is in the array.";
} else {
    echo "Jane is not in the array.";
}

Output:

Jane is in the array.

Example 4: Case-sensitive search

$colors = ["Red", "Blue", "Green"];

if (in_array("red", $colors)) {
    echo "Red is in the array.";
} else {
    echo "Red is not in the array.";
}

Output:

Red is not in the array.  // case-sensitive comparison

This function is handy when you need to check the existence of a value in an array without manually looping through it.