PHP in_array() Function (original) (raw)

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,arrayneedle, array needle,arrayhaystack, 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 needleisfoundinneedle is found in needleisfoundinhaystack.
• 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 `

`

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 `

`

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 `

`

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 `

`

Output

bool(false) bool(true)

4. Searching in Multidimensional Arrays

in_array() does not search inside nested arrays automatically:

PHP `

`

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

PHP `

`

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.