How to Use in_array in PHP: Syntax and Examples

In PHP, use in_array(value, array, strict) to check if a value exists in an array. It returns true if found, otherwise false. The optional strict parameter checks type equality.

Syntax

The in_array function checks if a value exists in an array.

• value: The item you want to find.
• array: The array to search in.
• strict (optional): If true, checks type too (default is false).

php

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

Example

This example shows how to check if a number or string is in an array using in_array. It also demonstrates the effect of the strict parameter.

php

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

// Check if 'banana' is in the array
if (in_array('banana', $fruits)) {
    echo "Banana is in the list.\n";
} else {
    echo "Banana is not in the list.\n";
}

// Check if number 5 is in the array of strings
$numbers = ['5', '10', '15'];

// Without strict, 5 (int) matches '5' (string)
if (in_array(5, $numbers)) {
    echo "5 found without strict check.\n";
}

// With strict, types must match
if (!in_array(5, $numbers, true)) {
    echo "5 not found with strict check.\n";
}
?>

Output

Banana is in the list.
5 found without strict check.
5 not found with strict check.

Common Pitfalls

One common mistake is forgetting the strict parameter, which can cause unexpected matches due to type juggling. For example, 5 (integer) matches '5' (string) if strict is false. Also, in_array only checks values, not keys.

php

<?php
// Wrong: no strict, may cause false positives
$values = ['0', '1', '2'];
if (in_array(false, $values)) {
    echo "Found false without strict (unexpected).\n";
}

// Right: use strict to avoid type confusion
if (!in_array(false, $values, true)) {
    echo "False not found with strict (expected).\n";
}
?>

Output

Found false without strict (unexpected).
False not found with strict (expected).

Quick Reference

Remember these tips when using in_array:

• Use strict=true to check both value and type.
• It returns true or false.
• It searches only values, not keys.
• Works with any array type: strings, numbers, objects.

Key Takeaways

Use in_array to check if a value exists in an array in PHP.

Set the strict parameter to true to avoid type-related mismatches.

in_array checks values only, not array keys.

It returns true if the value is found, otherwise false.

Always test your code to understand how type juggling affects results.