PHP crc32() Function

Complete PHP String Reference

Definition and Usage

The crc32() function calculates a 32-bit CRC (cyclic redundancy checksum) for a string.

This function can be used to validate data integrity.

Syntax

crc32(string)

Tips and Notes

Tip: To ensure that you get the correct string representation from the crc32() function, you'll need to use the %u formatter of the printf() or sprintf() function. If the %u formatter is not used, the result may display in incorrect and negative numbers.

Example 1

In this example we will print the result of crc32() with and without the "%u" formatter (note that the result is equal):

<?php
$str = crc32("Hello world!");
echo 'Without %u: '.$str."<br />";
echo 'With %u: ';
printf("%u",$str);
?> 

The output of the code above will be:

Without %u: 461707669
With %u: 461707669

Example 2

In this example we will print the result of crc32() with and without the "%u" formatter (note that the result is not equal):

<?php
$str = crc32("Hello world.");
echo 'Without %u: '.$str."<br />";
echo 'With %u: ';
printf("%u",$str);
?> 

The output of the code above will be:

Without %u: -1959132156
With %u: 2335835140

Complete PHP String Reference

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