Definition and Usage

PHP Version
4.0.5+

The array_search() function searches an array for a value.
It returns the key (or index) of the first matching element if found, or false if the value is not present.

Features

  • If the searched value is a string, the search is case-sensitive.
  • If multiple matches are found, only the key (or index) of the first matching value is returned.
  • If the third parameter is set to true, the search uses strict mode, which requires the data type to match exactly.
    By default, the number 2 and the string '2' are considered equal, but in strict mode, 2 and '2' are not equal.

Basic Example

PHP 
PHP
// Example 1: Using array_search() with a simple array
$arr = ['a', 'b', 'c'];

$key = array_search('c', $arr);
var_dump($key); // Output: int(2)

$notFound = array_search('d', $arr);
var_dump($notFound); // Output: bool(false)


// Example 2: Using array_search() with an associative array
$fruits = [
    'apple' => 'red',
    'banana' => 'yellow',
    'cherry' => 'red'
];

$colorToFind = array_search('red', $fruits);
var_dump($colorToFind); // Output: string(5) "apple"

Syntax

PHP 
array_search(mixed $needle, array $haystack, bool $strict = false): int|string|false

Parameters

Parameters of the array_search() Function
$needle The value to search for.
If it is a string, the comparison is case-sensitive.
$haystack The array in which to search.
$strict Optional. Determines whether the comparison should check for exact data type match (true or false).
  • If false, the number 2 and the string '2' are considered equal.
  • If true, the number 2 and the string '2' are not equal.

Return Values

If a match is found, array_search() returns the key (or index) of the first matching value. If no match is found, it returns false.

PHP 
$fruits = [
    'apple' => 'red',
    'banana' => 'yellow',
    'cherry' => 'red'
];

// Searches for the value 'red' in the $fruits array and returns the key (or index) of the first match
$colorToFind = array_search('red', $fruits);

// There are two keys with the value 'red' in the $fruits array: 'apple' and 'cherry'.
// $colorToFind is assigned the key of the first matching value ('red').
// Therefore, $colorToFind will be 'apple'.
var_dump($colorToFind); // Output: string(5) 'apple'

Important Note on Comparing Return Values

When using array_search(), always use the strict equality operator (===) to check the return value.

The following example shows the difference between using non-strict equality (==) and strict equality (===) to evaluate the search result.

PHP - Important Note 
$numbers = [0, "0", false, null];
$searchValue = 0;

$result = array_search($searchValue, $numbers, true);

if ($result == false) {
    echo "The value $searchValue was not found in the array.";
} else {
    echo "The value $searchValue is located at index $result.";
}

// Incorrect result!!!
// Output: 'The value 0 was not found in the array.'

if ($result === false) {
    echo "The value $searchValue was not found in the array.";
} else {
    echo "The value $searchValue is located at index $result.";
}

// Output: 'The value 0 is located at index 0.'

This example demonstrates how to search an array using array_search() and how to verify the result. The key point is understanding the difference between the two comparison methods:

  • In the first if statement, the non-strict equality operator (==) is used, which treats false and 0 as equal. This results in the incorrect message: "The value 0 was not found in the array."
  • In the second if statement, the strict equality operator (===) is used, which requires both the value and the data type to match. This avoids the incorrect message.

In conclusion, using the strict equality operator (===) ensures accurate evaluation of the return value and improves code reliability.

Practical Examples

The array_search() function is commonly used for the following purposes.

Searching for an Existing Value

PHP 
$numbers = [1, 2, 3, 4, 2, 5, 6];
$searchValue = 2;

if (array_search($searchValue, $numbers) !== false) {
    echo 'The value exists in the array.';
} else {
    echo 'The value does not exist in the array.';
}

// Output: 'The value exists in the array.'

This example demonstrates how to search for a value ($searchValue, here 2) in the $numbers array to check if it exists. The array_search() function returns the key (or index) of the first matching value if found, or false if not found. This code outputs: 'The value exists in the array.'

Deleting or Modifying a Found Value

PHP 
$products = [
    'apple' => 1.99,
    'banana' => 0.99,
    'cherry' => 2.49
];

$targetPrice = 1.00; // Price to search for

$key = array_search($targetPrice, $products);

if ($key !== false) {
    unset($products[$key]); // Remove the found value
    // Or modify the value: $products[$key] = new price;
} else {
    echo 'Product or price not found.';
}

In this example, the code searches for $targetPrice (1.00) and either removes or modifies the value in the array. array_search() checks if the product exists, and if found, deletion or modification is performed.

Searching in a Two-Dimensional Array

PHP 
$students = [
    ['name' => 'Alice', 'age' => 20],
    ['name' => 'Bob', 'age' => 22],
    ['name' => 'Charlie', 'age' => 21]
];

$searchName = 'Bob';

foreach ($students as $key => $student) {
    if (array_search($searchName, $student) !== false) {
        echo "Found student named $searchName. Student index: $key";
        break;
    }
}

// Output: 'Found student named Bob. Student index: 1'

Code Explanation
The foreach() loop is commonly used to iterate over arrays or objects.

In this example, we search for a student's name in the two-dimensional $students array and output the corresponding information. array_search() searches within each student array for the name, returning the student's index. Once found, the loop breaks and the student's information is displayed. This pattern is useful for student management or data lookup scenarios.

Finding the Position of a Specific Value in an Array

PHP 
$numbers = [3, 5, 2, 8, 10, 6];
$searchValue = 8;

$key = array_search($searchValue, $numbers);

if ($key !== false) {
    echo "The value $searchValue is located at index $key.";
} else {
    echo "The value $searchValue does not exist in the array.";
}

// Output: 'The value 8 is located at index 3.'

References

See also