PHP Variable Handling is_iterable() Function

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The PHP Variable Handling is_iterable() function is used to check whether a variable can be used in a loop. It was first added to PHP 7.1 and is also compatible with PHP 8. This function checks whether a variable is an array or a loopable object. If a variable is iterable, we can use foreach to iterate over its values.

Using loops will fail if the item cannot be iterated. It is useful for working with functions that need iterable input. It reduces errors by checking whether a value can be looped. This function increases code dependability. It is simple and straightforward to use.

Syntax

Below is the syntax of the PHP Variable Handling is_iterable() function −

bool is_iterable ( mixed $value )

Parameters

This function accepts $value parameter which is the variable that we want to check if it is iterable.

Return Value

The is_iterable() function returns TRUE if the variable is an array or an object that can be looped. And it returns FALSE if the variable is not iterable.

PHP Version

First introduced in core PHP 7.1.0, the is_iterable() function continues to function easily in PHP 8.

Example 1

Here is the basic example of the PHP Variable Handling is_iterable() function to check if an array is iterable. As arrays are iterable so it will return true.

<?php
   // An array
   $myArray = [1, 2, 3, 4]; 
   if (is_iterable($myArray)) {
      echo "The variable is iterable."; 
   } else {
      echo "The variable is not iterable.";
   }
?>

Output

Here is the outcome of the following code −

The variable is iterable.

Example 2

In the below PHP code we will use the is_iterable() function and check a non iterable variable. So the program will check a string which is not iterable. So it will return false.

<?php
   // A string (not iterable)
   $myString = "Hello"; 
   if (is_iterable($myString)) {
      echo "The variable is iterable.";
   } else {
      echo "The variable is not iterable."; 
   }
?> 

Output

This will generate the below output −

The variable is not iterable.

Example 3

Now the below code uses the is_iterable() function inside a user defined function. So the function takes an input and loops over it only if it is iterable by preventing errors.

<?php
   function printItems($data) {
      if (is_iterable($data)) {
         foreach ($data as $item) {
            echo $item . " ";
         }
      } else {
         echo "The input is not iterable.";
      }
   }

   printItems([100, 200, 300]);
   echo "\n";
   printItems("Not an array");
?> 

Output

This will create the below output −

100 200 300 
The input is not iterable.