PHP in_array() Function - Scientech Easy

The in_array() function in PHP is a built-in function that checks if a specific value exists in an array or not. You can use this function when you want to verify the existence of a value in an array.

In simple words, the in_array() function search an array for a specific value. The general syntax of the in_array() function in PHP is as follows:

in_array(mixed $needle, array $haystack, bool $strict = false): bool

In the above syntax of the in_array() function, there are three parameters:

$needle (required): This parameter represents the value to search for in the array.
$haystack (required): This parameter is the array in which the function will search for the specified value.
$strict (optional): If this parameter is set to true, the function will also check the data types of the values, performing a strict comparison (===).

The in_array() function returns true if the value is found. If not found, it returns false value.

Basic Examples of PHP in_array() Function

Example 1: Let’s write a PHP program in which we will check a string exists in an array or not.

<?php
$fruits = ["apple", "banana", "cherry", "orange"];

if (in_array("orange", $fruits)) {
     echo "Orange is in the list.";
} else {
     echo "Orange is not in the list.";
}
?>

Output:
      Orange is in the list.

Example 2: Let’s write a PHP program to check a number exists in an array or not.

<?php
$numbers = [10, 20, 30, 40, 50];

if (in_array(30, $numbers)) {
     echo "30 is present in the list.";
} else {
     echo "30 is not present in the list.";
}
?>

Output:
      30 is present in the list.

Using the Strict Parameter

By default (i.e. when set to false), the in_array() function uses loose comparison (==). This can sometimes lead to unexpected results if data types are not considered. Look at the below examples.

Example 3: Loose Comparison (strict = false)

<?php
$values = [1, 2, "3", 4];

if (in_array(3, $values)) {
    echo "Value 3 is found without strict.";
}
?>

Output:
      Value 3 is found without strict.

In this example, the integer value 3 is equal to string value “3” because of using loose comparison.

Example 4: With strict comparison (strict = true)

<?php
$values = [1, 2, "3", 4];

if (in_array(3, $values, true)) {
    echo "Value 3 is found without strict.";
} else {
    echo "Value 3 is not found with strict.";
}
?>

Output:
       Value 3 is not found with strict.

In this example, PHP uses strict comparison due to which the integer 3 is not identical to string value “3”.

Checking for Values in Associative Array

The in_array() function only checks values, not keys in an associative array.

Example 5: Associative array

<?php
$person = [
    "name" => "Saanvi",
    "age" => 25,
    "country" => "USA"
];
if (in_array("USA", $person)) {
    echo "Country is USA.";
}
?>

Output:
       Country is USA.

If you want to check for keys, use the array_key_exists() function instead of in_array() function provided by PHP.

Case-insensitive Search with PHP’s in_array() Function

The in_array() function in PHP is case-sensitive by default, which can lead to unexpected results if you’re not aware of this behavior. Let’s take an example to understand case-insensitive searches.

Example 6:

<?php
$colors = ['Red', 'Green', 'Blue', 'Yellow'];

if (in_array('yellow', $colors)) {
    echo 'Found yellow!';
} else {
    echo 'Yellow not found!'; // This will be executed.
}
?>

Output:
      Yellow not found!

In this example, the in_array() function returns false because the value ‘yellow’ which is in lowercase, doesn’t match the ‘Yellow’ in the array.

Solutions for Case-Insensitive Search

To make the in_array() function case-insensitive, you can convert both the array values and the search value to lowercase using array_map() and strtolower() before comparison.

Example 7:

<?php
$colors = ['Red', 'Green', 'Blue', 'Yellow'];

// Convert all array values to lowercase.
$lowercaseColors = array_map('strtolower', $colors);

// Search for lowercase 'yellow'.
if(in_array(strtolower('yellow'), $lowercaseColors)) {
     echo 'Found yellow!';
} else {
     echo 'Yellow not found!';
}
?>

Output:
      Found yellow!

In this example, the array_map(‘strtolower’, $colors) function converts all values in the array to lowercase. The strtolower(‘yellow’) function also converts the search term into lowercase. Thus, this makes the search case-insensitive.

Searching in Multidimensional Arrays in PHP Using in_array()

The in_array() function in PHP only searches for a value in one-dimensional arrays. If you try to use it directly on a multidimensional array, it won’t work as expected because each element in the outer array is itself an array (or sub-array), not a simple value.

To search within a value from a multidimensional array, you need to loop through each sub-array and use in_array() within the loop. Let’s take an example on it.

Example 8:

<?php
$users = [
     ["id" => 1, "name" => "Saanvi"],
     ["id" => 2, "name" => "Tripti"],
     ["id" => 3, "name" => "Bob"]
];
$searchName = "Tripti";
$found = false;

foreach ($users as $user) {
   if (in_array($searchName, $user)) {
      $found = true;
      break;
   }
}
if ($found) {
    echo "User '$searchName' found.";
} else {
    echo "User '$searchName' not found.";
}
?>

Output:
      User 'Tripti' found.

In this example, $users is a multidimensional array, which is an array of associative arrays. Then, we have looped over each sub-array. The in_array($searchName, $user) function checks if the value exists in that sub-array. If found, we break out of the loop and set $found to true. After that, we have used if-else statement.

The in_array() function in PHP is used for checking if a value exists in an array. If you have a simple search, use this function. You should use the third parameter (strict) if you want to match data type as well as value. I hope that you will have understood the basic concepts of in_array() function and practiced all examples based on it.