Understanding PHP Array Length with Practical Examples

php array length

When working with arrays in PHP, one of the most common questions is: how do I get the PHP array length? In PHP, "array length" usually means the number of elements inside an array. This short guide explains the standard functions and a few helpful tips so you can use php array length correctly in your projects.

Primary ways to get PHP array length

The most common functions are count() and sizeof(). They behave the same for arrays:

1) count()

count() returns the number of items in an array (or properties in an object that implements Countable).

<?php
$items = ['apple', 'banana', 'cherry'];
echo count($items); // outputs: 3
?>
    

2) sizeof()

sizeof() is an alias of count(). Use either one; most developers prefer count() for clarity.

<?php
$items = ['apple', 'banana', 'cherry'];
echo sizeof($items); // outputs: 3
?>
    

Counting elements in multidimensional arrays

By default, count() counts only top-level elements. To count recursively (all elements in nested arrays), use count($array, COUNT_RECURSIVE).

<?php
$matrix = [
    ['a', 'b'],
    ['c', 'd', 'e']
];

echo count($matrix); // outputs: 2  (two sub-arrays)
echo count($matrix, COUNT_RECURSIVE); // outputs: 7 (includes nested elements)
?>
    

Counting iterator objects

If you have an object that implements Iterator (e.g., ArrayObject), count() works if it implements Countable. For general iterators, you can use iterator_count() to consume the iterator and get its length.

<?php
$it = new ArrayIterator([1,2,3,4]);
echo $it->count(); // outputs: 4

// For a generic iterator:
$generator = (function() { yield 1; yield 2; yield 3; })();
echo iterator_count($generator); // outputs: 3
?>
    

Common pitfalls when getting PHP array length

• Counting non-arrays: count(null) returns 0, but calling count() on something that isn't an array or Countable may be a sign of a bug. Validate types when needed.
• Recursive counting surprises: COUNT_RECURSIVE counts the parent arrays as well — adjust your logic if you only want leaf nodes.
• Large arrays and performance: Counting is O(1) for PHP arrays (stored size), but converting or iterating over very large structures repeatedly can cost memory/time.

Practical examples (useful snippets)

Example: Check if array is empty

<?php
$items = [];
if (count($items) === 0) {
    echo 'Array is empty';
}
?>
    

Example: Get last index of numeric array

<?php
$colors = ['red','green','blue'];
$length = count($colors); // 3
$lastIndex = $length - 1; // 2
echo $colors[$lastIndex]; // outputs: blue
?>
    

Best practices & tips

• Prefer count() for clarity; sizeof() is equivalent but less explicit.
• When you need a boolean check for emptiness, empty($array) or !count($array) both work — prefer empty() for readability.
• Avoid repeatedly calling count() inside loops — store the value in a variable if the array size won't change during the loop.

Conclusion

Getting php array length is straightforward with count() and sizeof(). For nested arrays use COUNT_RECURSIVE, and for iterators consider iterator_count(). Use these tools carefully and follow best practices to avoid common pitfalls.

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