How to Avoid Losing Precision When Parsing JSON with json_decode?

gitbox 2025-09-12

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echo "<h1>How to Avoid Losing Precision When Parsing JSON with json_decode?</h1>";</p>
<p>echo <span><span class="hljs-string">"<p>In PHP, using <code>json_decode

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The result might show inaccurate numbers, expressed in scientific notation or with trailing digits missing.

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Solution

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The core idea for solving this issue is to treat large numbers as strings, rather than parsing them as integers or floats. The following methods are commonly used:

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Method 1: Use the JSON_BIGINT_AS_STRING Option

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$data = json_decode($json, true, 512, JSON_BIGINT_AS_STRING);\nvar_dump($data);

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The JSON_BIGINT_AS_STRING option converts numbers larger than PHP's integer range into strings, avoiding precision loss.

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Method 2: Convert Large Numbers to Strings at the JSON Generation Stage

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If you control the generation of the JSON data, you can wrap large numbers in quotes during JSON creation:

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{"big_number": "12345678901234567890"}

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This way, PHP will directly receive them as strings, avoiding precision loss during parsing.

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Method 3: Use Arbitrary Precision Math Libraries

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If mathematical operations need to be performed on large numbers, you can use PHP's bcmath or gmp extensions:

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$bigNumber = $data['big_number'];\necho bcadd($bigNumber, '1');

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This allows calculations with arbitrary precision, preventing floating-point precision issues.

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Conclusion

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PHP may lose precision when parsing large integers in JSON.

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Using JSON_BIGINT_AS_STRING or converting numbers to strings beforehand are common solutions.

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If mathematical operations are required, it's recommended to use bcmath or gmp extensions.

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json_decode