PHP in_array() Function

Last Updated : 02 Jun, 2025

The in_array() function in PHP is a built-in function that is used to check if a specific value exists within an array and returns a boolean result. Returns true if the value is found and false if the value is not found.

Syntax:

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

In this syntax:

$needle (mixed): The value to search for in the array.
$haystack (array): The array in which to search.
$strict (bool, optional): If set to true, the function will also check the types of the $needle and the array elements.
Defaults to false (non-strict comparison).

Return Value

Returns true if $needle is found in $haystack.
Returns false if $needle is not found.

How in_array() Works?

The in_array() function in the PHP works in the following ways:

By default, in_array() performs a loose comparison (==) between $needle and the array elements.
If $strict is true, it performs a strict comparison (===) which checks both the value and the type.
This behavior is important when searching in arrays with mixed types (e.g., strings, integers, floats).

Now, let us understand with the help of the example:

PHP


  $fruits = ["apple", "banana", "orange"];
if (in_array("banana", $fruits)) {
    echo "Banana is in the list!";
} else {
    echo "Banana is not found.";
}
?>

Output

Banana is in the list!

1. Using in_array() with Numbers

This example demonstrates how in_array() checks for both numeric and string values in an array using loose comparison.

PHP


$numbers = [1, 2, 3, "4"];
var_dump(in_array(3, $numbers));      
var_dump(in_array("4", $numbers));    
var_dump(in_array(5, $numbers));      
?>

Output

bool(true)
bool(true)
bool(false)

2. Strict Type Checking

This example illustrates how in_array() uses strict mode to compare both value and type when searching in an array.

PHP


 $numbers = [1, 2, 3, "4"];
var_dump(in_array(4, $numbers, true));   
var_dump(in_array("4", $numbers, true));  
?>

Output

bool(false)
bool(true)

3. Case Sensitivity

This example highlights in_array()’s case-sensitive behavior when searching for string values inside an array.

PHP


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

var_dump(in_array("red", $colors));  // false, "red" != "Red"
var_dump(in_array("Red", $colors));  // true

?>

Output

bool(false)
bool(true)

4. Searching in Multidimensional Arrays

in_array() does not search inside nested arrays automatically:

PHP


  $array = [
    ["id" => 1, "name" => "anjali"],
    ["id" => 2, "name" => "arti"]
];
var_dump(in_array("anjali", $array));  
?>

Output

bool(false)

To search deeply in multidimensional arrays, you need to use custom functions or array functions like array_column():

PHP


  if (is_array($array)) {
    $names = array_column($array, 'name');
    if (in_array("anjali", $names)) {
        echo "anjali is found!";
    }
} else {
    echo "Input data is not valid.";
}
?>

Output

Input data is not valid.

Common Use Cases for in_array()

Form validation: Check if a submitted value is among the allowed options.
User permissions: Verify if a user role exists in the allowed roles array.
Filtering: Decide whether to include/exclude elements based on a list.
Control flow: Execute code conditionally based on presence of values.

Best Practices

Use the $strict parameter to avoid unexpected matches, especially when working with numeric strings and integers.
For multidimensional arrays, consider flattening or using array functions like array_column().
For case-insensitive checks, manually normalize the case before searching.
Remember that in_array() only searches the first-level array elements.

Conclusion

The PHP in_array() function is a straightforward and handy tool for checking if a value exists within an array. Its flexibility with the optional strict type checking and compatibility with various data types make it a staple in PHP programming. Remember its limitations in multidimensional arrays and case sensitivity to use it effectively.

PHP in_array() Function

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Article Tags :

PHP in_array() Function

Syntax:

Return Value

How in_array() Works?

1. Using in_array() with Numbers

2. Strict Type Checking

3. Case Sensitivity

4. Searching in Multidimensional Arrays

Common Use Cases for in_array()

Best Practices

Conclusion

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