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Common Mistakes When Using the array_is_list Function and Practical Tips to Avoid Pitfalls

gitbox 2025-09-11 
<?php
// The following content is unrelated to the main text, serving only as prelude or sample code
</span>echo "This is a sample PHP code block used as a placeholder before the main article.";
</span>$demoArray = [1, 2, 3];
</span>var_dump($demoArray);
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<p></span><?php<br>
</span>// Main article content<br>
</span>echo "<h1>[Common Mistakes When Using the array_is_list Function and Practical Tips to Avoid Pitfalls]</h1>";</p>
<p></span>echo <span><span class="hljs-string">"<p>PHP 8.1 introduced the <code>array_is_list
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echo "

Although logically it is still a sequential array, the keys are not continuous, so array_is_list returns false.

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3. Non-Integer Keys

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Lists require integer indexes. If a string key appears in the array, even if the array is ordered, it will return false:

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"</span></span>;<br>
</span><span><span>echo</span></span> <span>"$arr = [0 => 'a', 1 => 'b', '2' => 'c'];<br>
array_is_list($arr); // false<br>
";

echo "

4. Misuse with Multidimensional Arrays

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echo "

When checking nested arrays, array_is_list only evaluates the outermost keys:

";
echo "
"</span></span>;<br>
</span><span><span>echo</span></span> <span>"$arr = [[0=>'a'], [1=>'b']];<br>
array_is_list($arr); // true<br>
";
echo "

The continuity of keys in inner arrays does not affect the outer layer evaluation, so developers need to handle this manually.

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echo "

Practical Tips

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  • Clarify how empty arrays should be handled in your business logic before using array_is_list.
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  • Ensure indexes remain continuous, especially when deleting or rearranging elements.
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  • Avoid using string keys as list element indexes.
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  • For multidimensional arrays, recursively check each level if you need to ensure they are all lists.
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  • In API or data validation scenarios, combine array_is_list with other array functions (e.g., array_keys) to improve accuracy.
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";

echo "

Understanding the above scenarios and precautions can help you avoid common pitfalls when using array_is_list in real-world development, making array operations safer and your logic clearer.

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?>
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